diff --git a/libwvdrmengine/cdm/core/include/cdm_engine.h b/libwvdrmengine/cdm/core/include/cdm_engine.h
index 90a74b8c..a29c46b9 100644
--- a/libwvdrmengine/cdm/core/include/cdm_engine.h
+++ b/libwvdrmengine/cdm/core/include/cdm_engine.h
@@ -212,6 +212,15 @@ class CdmEngine {
   // system. This will force the device to reprovision itself.
   virtual CdmResponseType Unprovision(CdmSecurityLevel security_level);
 
+  // Remove the system's REE-side OEM certificate for the specified
+  // |security_level|.
+  // Only effects two-stage provisioning devices which have an OEM cert
+  // in the REE side file system.
+  // Removing the OEM certificate will cause all DRM certificates tied to
+  // the OEM certificate to be invalidated and unloadable to future
+  // sessions.
+  virtual CdmResponseType UnprovisionOemCert(CdmSecurityLevel security_level);
+
   // Return the list of key_set_ids stored on the current (origin-specific)
   // file system.
   virtual CdmResponseType ListStoredLicenses(
diff --git a/libwvdrmengine/cdm/core/include/certificate_provisioning.h b/libwvdrmengine/cdm/core/include/certificate_provisioning.h
index 52d35fd6..be2d7d0d 100644
--- a/libwvdrmengine/cdm/core/include/certificate_provisioning.h
+++ b/libwvdrmengine/cdm/core/include/certificate_provisioning.h
@@ -72,6 +72,28 @@ class CertificateProvisioning {
   // |default_url| by GetProvisioningRequest().
   static void GetProvisioningServerUrl(std::string* default_url);
 
+  enum State {
+    // Freshly created, not yet initialized.
+    kUninitialized,
+    // A successful call to Init() has been made.
+    kInitialized,
+    // Has generated a DRM request; apps are allowed generate
+    // another one even if a response has not been received.
+    kDrmRequestSent,
+    // Has received (and successfully loaded) a DRM response.
+    kDrmResponseReceived,
+    // Has generated an OEM (Prov 4.0) request; apps are allowed
+    // generate another one even if a response has not been
+    // received.
+    kOemRequestSent,
+    // Has received (and successfully loaded) an OEM response.
+    kOemResponseReceived,
+  };
+  static const char* StateToString(State state);
+
+  // State setter for testing only.
+  void SetStateForTesting(State state) { state_ = state; }
+
  private:
 #if defined(UNIT_TEST)
   friend class CertificateProvisioningTest;
@@ -122,22 +144,31 @@ class CertificateProvisioning {
   CdmResponseType CloseSessionOnError(CdmResponseType status);
   void CloseSession();
 
+  // Tracks the state of CertificateProvisioning.
+  State state_ = kUninitialized;
+
   std::unique_ptr<CryptoSession> crypto_session_;
   CdmCertificateType cert_type_;
   std::unique_ptr<ServiceCertificate> service_certificate_;
   std::string request_;
+
+  // == Provisioning 4.0 Variables ==
   // The wrapped private key in provisioning 4 generated by calling
   // GenerateCertificateKeyPair. It will be saved to file system if a valid
   // response is received.
-  std::string provisioning_40_wrapped_private_key_;
-  // Key type of the generated key pair in provisioning 4.
-  CryptoWrappedKey::Type provisioning_40_key_type_;
-  // Store the last provisioning request message
-  std::string provisioning_request_message_;
+  CryptoWrappedKey prov40_wrapped_private_key_;
+  // Cache of the most recently sent OEM/DRM public key sent.  Used
+  // to match the response with the request.
+  // This MUST be matched with the current |prov40_wrapped_private_key_|.
+  std::string prov40_public_key_;
+
+  // Store the last provisioning request message.
+  // This is the serialized ProvisioningRequest.
+  // Used for X.509 responses which require the original
+  // request to verify the signature of the response.
+  std::string prov40_request_;
 
   CORE_DISALLOW_COPY_AND_ASSIGN(CertificateProvisioning);
-};
-
+};  // class CertificateProvisioning
 }  // namespace wvcdm
-
 #endif  // WVCDM_CORE_CERTIFICATE_PROVISIONING_H_
diff --git a/libwvdrmengine/cdm/core/include/crypto_wrapped_key.h b/libwvdrmengine/cdm/core/include/crypto_wrapped_key.h
index bf947bb9..3dfe045f 100644
--- a/libwvdrmengine/cdm/core/include/crypto_wrapped_key.h
+++ b/libwvdrmengine/cdm/core/include/crypto_wrapped_key.h
@@ -5,6 +5,7 @@
 #define WVCDM_CORE_CRYPTO_WRAPPED_KEY_H_
 
 #include <string>
+#include <utility>
 
 namespace wvcdm {
 
@@ -18,6 +19,8 @@ class CryptoWrappedKey {
   CryptoWrappedKey() {}
   CryptoWrappedKey(Type type, const std::string& key)
       : type_(type), key_(key) {}
+  CryptoWrappedKey(Type type, std::string&& key)
+      : type_(type), key_(std::move(key)) {}
 
   Type type() const { return type_; }
   void set_type(Type type) { type_ = type; }
@@ -26,6 +29,7 @@ class CryptoWrappedKey {
   // Mutable reference getter for passing to OMECrypto.
   std::string& key() { return key_; }
   void set_key(const std::string& key) { key_ = key; }
+  void set_key(std::string&& key) { key_ = std::move(key); }
 
   void Clear() {
     type_ = kUninitialized;
diff --git a/libwvdrmengine/cdm/core/include/wv_cdm_types.h b/libwvdrmengine/cdm/core/include/wv_cdm_types.h
index e4847271..605ec668 100644
--- a/libwvdrmengine/cdm/core/include/wv_cdm_types.h
+++ b/libwvdrmengine/cdm/core/include/wv_cdm_types.h
@@ -465,6 +465,9 @@ enum CdmResponseEnum : int32_t {
   GET_DEVICE_INFORMATION_ERROR = 398,
   GET_DEVICE_SIGNED_CSR_PAYLOAD_ERROR = 399,
   GET_TOKEN_FROM_EMBEDDED_CERT_ERROR = 400,
+  PROVISIONING_UNEXPECTED_RESPONSE_ERROR = 402,
+  PROVISIONING_4_STALE_RESPONSE = 403,
+  PROVISIONING_4_FAILED_TO_VERIFY_CERT_KEY = 404,
   // Don't forget to add new values to
   //  * core/src/wv_cdm_types.cpp
   //  * android/include/mapErrors-inl.h
diff --git a/libwvdrmengine/cdm/core/src/cdm_engine.cpp b/libwvdrmengine/cdm/core/src/cdm_engine.cpp
index 3d8ed126..343377f9 100644
--- a/libwvdrmengine/cdm/core/src/cdm_engine.cpp
+++ b/libwvdrmengine/cdm/core/src/cdm_engine.cpp
@@ -1286,6 +1286,13 @@ CdmResponseType CdmEngine::HandleProvisioningResponse(
     LOGE("Device has been revoked, cannot provision: status = %s",
          ret.ToString().c_str());
     cert_provisioning_.reset();
+  } else if (ret == PROVISIONING_4_STALE_RESPONSE) {
+    // The response is considered "stale" (likely from generating multiple
+    // requests, and providing out of order responses).
+    // Drop message without returning error or resetting
+    // provisioning context.
+    LOGW("Stale response, app may try again");
+    return CdmResponseType(NO_ERROR);
   } else {
     // It is possible that a provisioning attempt was made after this one was
     // requested but before the response was received, which will cause this
@@ -1332,8 +1339,7 @@ CdmProvisioningStatus CdmEngine::GetProvisioningStatus(
     return kUnknownProvisionStatus;
   }
 
-  UsagePropertySet property_set;
-  if (handle.HasCertificate(property_set.use_atsc_mode())) {
+  if (handle.HasCertificate(/* atsc_mode_enabled = */ false)) {
     return kProvisioned;
   }
   if (crypto_session->GetPreProvisionTokenType() == kClientTokenBootCertChain) {
@@ -1356,8 +1362,8 @@ CdmResponseType CdmEngine::Unprovision(CdmSecurityLevel security_level) {
     LOGD("OKP fallback to L3");
     security_level = kSecurityLevelL3;
   }
-  // Devices with baked-in DRM certs cannot be reprovisioned and therefore must
-  // not be unprovisioned.
+  // Devices with baked-in DRM certs cannot be reprovisioned
+  // and therefore must not be unprovisioned.
   std::unique_ptr<CryptoSession> crypto_session(
       CryptoSession::MakeCryptoSession(metrics_->GetCryptoMetrics()));
   CdmClientTokenType token_type = kClientTokenUninitialized;
@@ -1376,18 +1382,78 @@ CdmResponseType CdmEngine::Unprovision(CdmSecurityLevel security_level) {
     LOGE("Unable to initialize device files");
     return CdmResponseType(UNPROVISION_ERROR_1);
   }
-
-  // TODO(b/141705730): Remove usage entries during unprovisioning.
-  if (!file_system_->IsGlobal()) {
-    if (!handle.RemoveCertificate() || !handle.RemoveOemCertificate()) {
-      LOGE("Unable to delete certificate");
+  // This if statement is misleading.  There is no consistent
+  // concept of "global" vs "per-app/origin" storage in the
+  // core library.  Android vs CE CDM behave very different.
+  // On CE device:
+  //    file_system_->IsGlobal() is always true, even if app/origin
+  //    specific.
+  // On Android:
+  //    file_system_->IsGlobal() is always false, except for some C++
+  //    test code.
+  // TODO(b/142280599): Refactor this once CE CDM SPOIDs are supported
+  // by the file system.  May require moving platform-dependent behavior
+  // to the platform-dependent layer.  Only have this remove the
+  // certificate and nothing else.
+  if (!file_system_->IsGlobal()) {  // AKA is Android
+    // TODO(b/141705730): Remove usage entries during unprovisioning.
+    // Not considered an error if no certificate exists.
+    if (handle.HasCertificate(/* atsc_mode_enabled = */ false) &&
+        !handle.RemoveCertificate()) {
+      LOGE("Unable to delete DRM certificate");
       return CdmResponseType(UNPROVISION_ERROR_2);
     }
+    // Maintaining old behavior expected by Android.
+    const CdmResponseType oem_cert_status = UnprovisionOemCert(security_level);
+    if (oem_cert_status != NO_ERROR) return oem_cert_status;
+  } else {  // AKA is CE CDM (or some Android tests)
+    // On CE CDM, deleting all files only deletes the app/origin
+    // specific files.
+    // On Android, this will delete all files (only possible
+    // during testing).
+    if (!handle.DeleteAllFiles()) {
+      LOGE("Unable to delete files");
+      return CdmResponseType(UNPROVISION_ERROR_3);
+    }
+  }
+  return CdmResponseType(NO_ERROR);
+}
+
+CdmResponseType CdmEngine::UnprovisionOemCert(CdmSecurityLevel security_level) {
+  LOGI("security_level = %s", CdmSecurityLevelToString(security_level));
+  if (security_level == kSecurityLevelL1 && OkpIsInFallbackMode()) {
+    LOGD("OKP fallback to L3");
+    security_level = kSecurityLevelL3;
+  }
+  // Only BCC-based system have an OEM certificate that can
+  // unprovisioned.
+  // Prov 3.0 system's OEM certs are built into the TEE.
+  std::unique_ptr<CryptoSession> crypto_session(
+      CryptoSession::MakeCryptoSession(metrics_->GetCryptoMetrics()));
+  CdmClientTokenType token_type = kClientTokenUninitialized;
+  const CdmResponseType res = crypto_session->GetProvisioningMethod(
+      security_level == kSecurityLevelL3 ? kLevel3 : kLevelDefault,
+      &token_type);
+  if (res != NO_ERROR) {
+    return res;
+  }
+  if (token_type != kClientTokenBootCertChain) {
+    LOGD("Device does not support OEM certificate unprovisioning");
     return CdmResponseType(NO_ERROR);
   }
-  if (!handle.DeleteAllFiles()) {
-    LOGE("Unable to delete files");
-    return CdmResponseType(UNPROVISION_ERROR_3);
+  // For Prov 4.0 devices, this will cause every app/origin client
+  // to lose their offline content for the same TEE security level.
+  wvutil::FileSystem global_file_system;
+  DeviceFiles global_handle(&global_file_system);
+  if (!global_handle.Init(security_level)) {
+    LOGE("Unable to initialize global device files");
+    return CdmResponseType(UNPROVISION_ERROR_1);
+  }
+  // Not considered an error if no certificate exists.
+  if (global_handle.HasOemCertificate() &&
+      !global_handle.RemoveOemCertificate()) {
+    LOGE("Unable to delete OEM certificate");
+    return CdmResponseType(UNPROVISION_ERROR_2);
   }
   return CdmResponseType(NO_ERROR);
 }
diff --git a/libwvdrmengine/cdm/core/src/certificate_provisioning.cpp b/libwvdrmengine/cdm/core/src/certificate_provisioning.cpp
index b40c3825..bf853b66 100644
--- a/libwvdrmengine/cdm/core/src/certificate_provisioning.cpp
+++ b/libwvdrmengine/cdm/core/src/certificate_provisioning.cpp
@@ -1,9 +1,10 @@
 // Copyright 2018 Google LLC. All Rights Reserved. This file and proprietary
 // source code may only be used and distributed under the Widevine License
 // Agreement.
-
 #include "certificate_provisioning.h"
 
+#include <algorithm>
+
 #include "client_identification.h"
 #include "crypto_wrapped_key.h"
 #include "device_files.h"
@@ -87,6 +88,127 @@ bool RetrieveOemCertificateAndLoadPrivateKey(CryptoSession& crypto_session,
   return true;
 }
 
+// Checks if any instances of |needle| sequences found in the |haystack|.
+//
+// Special cases:
+//  - An empty |needle| is always present, even if |haystack| is empty.
+//    Note: This is a convention used by many string utility
+//    libraries.
+bool StringContains(const std::string& haystack, const std::string& needle) {
+  if (needle.empty()) return true;
+  if (haystack.size() < needle.size()) return false;
+  return haystack.find(needle) != std::string::npos;
+}
+
+// Checks if the |needle| sequences found at the end of |haystack|.
+//
+// Special cases:
+//  - An empty |needle| is always present, even if |haystack| is empty.
+//    Note: This is a convention used by many string utility
+//    libraries.
+bool StringEndsWith(const std::string& haystack, const std::string& needle) {
+  if (haystack.size() < needle.size()) return false;
+  return std::equal(haystack.rbegin(), haystack.rbegin() + needle.size(),
+                    needle.rbegin(), needle.rend());
+}
+
+// Checks the actual length of an ASN.1 DER encoded message
+// roughly matches the expected length from within the message.
+// Technically, the DER message may contain some trailing
+// end-of-contents bytes (at most 2).
+//
+// Parameters:
+//  |actual_length| - The real length of the DER message
+//  |expected_length| - The reported length of the DER message plus
+//                      the header bytes parsed.
+bool IsAsn1ExpectedLength(size_t actual_length, size_t expected_length) {
+  return actual_length >= expected_length &&
+         actual_length <= (expected_length + 2);
+}
+
+// Checks if the provided |message| resembles ASN.1 DER encoded
+// message.
+// This is a light check, it verifies the type (SEQUENCE) and that
+// the encoded length matches the total message length.
+bool IsAsn1DerSequenceLike(const std::string& message) {
+  // Anything less than 3 bytes will not be an ASN.1 sequence.
+  if (message.size() < 3) return false;
+  // Verify type header
+  //  class = universal(0) - bits 6-7
+  //  p/c = constructed(1) - bit 5
+  //  tag = sequence(0x10) - bits 0-4
+  static constexpr uint8_t kUniversal = (0 << 6);
+  static constexpr uint8_t kConstructBit = (1 << 5);
+  static constexpr uint8_t kSequenceTag = 0x10;
+  static constexpr uint8_t kSequenceHeader =
+      kUniversal | kConstructBit | kSequenceTag;
+  const uint8_t type_header = static_cast<uint8_t>(message.front());
+  if (type_header != kSequenceHeader) return false;
+
+  // Verify length.
+  const uint8_t length_header = static_cast<uint8_t>(message[1]);
+  // A reserved length is never used.  If |length_header| is
+  // reserved length, then this is not an ASN.1 message.
+  static constexpr uint8_t kReservedLength = 0xff;
+  if (length_header == kReservedLength) return false;
+
+  static constexpr uint8_t kIndefiniteLength = 0x80;
+  if (length_header == kIndefiniteLength) {
+    // If length is indefinite, then search for two "end of contents"
+    // octets at the end.
+    static constexpr uint8_t kAsnEndOfContents = 0x00;
+    const std::string kDoubleEoc(2, kAsnEndOfContents);
+    return StringEndsWith(message, kDoubleEoc);
+  }
+
+  // Definite lengths may be long or short (most likely long for our case).
+  static constexpr uint8_t kLongLengthBit = 0x80;
+
+  if ((length_header & kLongLengthBit) != kLongLengthBit) {
+    // Short length (unlikely, but check anyways).
+    // For short lengths, the value component of the length
+    // header is the payload length.
+    static constexpr uint8_t kShortLengthMask = 0x7f;
+    const size_t payload_length =
+        static_cast<size_t>(length_header & kShortLengthMask);
+
+    // The total message is: type header + length header + payload.
+    const size_t total_length = 2 + payload_length;
+    return IsAsn1ExpectedLength(message.size(), total_length);
+  }
+
+  // Long length.
+  // |length_header| contains the number of bytes following the
+  // length header containing the payload length.
+  static constexpr uint8_t kLengthSizeMask = 0x7f;
+  const size_t length_length =
+      static_cast<size_t>(length_header & kLengthSizeMask);
+  // For long-lengths, the first two bytes were type header and
+  // length header.
+  static constexpr size_t kPayloadLengthOffset = 2;
+  // If the message is smaller than needed to obtain the length,
+  // it is either not ASN.1 (or an incomplete message, which is still
+  // invalid).
+  if ((message.size()) < (length_length + kPayloadLengthOffset)) return false;
+  // DER encoding should use the minimum number of bytes necessary
+  // to encode the length, and if the number of bytes to encode the
+  // length is more than 3 (payload is larged than 16 MB) which is much
+  // larger than any expected certificate chain.
+  if (length_length > 3) return false;
+
+  // Decode the length as big-endian.
+  size_t payload_length = 0;
+  for (size_t i = 0; i < length_length; i++) {
+    // Casting from char to uint8_t to size_t is necessary.
+    const uint8_t length_byte =
+        static_cast<uint8_t>(message[kPayloadLengthOffset + i]);
+    payload_length = (payload_length << 8) + static_cast<size_t>(length_byte);
+  }
+
+  // Total message is: type header + length header + payload length + payload.
+  const size_t total_length = 2 + length_length + payload_length;
+  return IsAsn1ExpectedLength(message.size(), total_length);
+}
 }  // namespace
 // Protobuf generated classes.
 using video_widevine::DrmCertificate;
@@ -98,6 +220,25 @@ using video_widevine::PublicKeyToCertify;
 using video_widevine::SignedDrmCertificate;
 using video_widevine::SignedProvisioningMessage;
 
+// static
+const char* CertificateProvisioning::StateToString(State state) {
+  switch (state) {
+    case kUninitialized:
+      return "Uninitialized";
+    case kInitialized:
+      return "Initialized";
+    case kDrmRequestSent:
+      return "DrmRequestSent";
+    case kDrmResponseReceived:
+      return "DrmResponseReceived";
+    case kOemRequestSent:
+      return "OemRequestSent";
+    case kOemResponseReceived:
+      return "OemResponseReceived";
+  }
+  return "<unknown>";
+}
+
 // static
 void CertificateProvisioning::GetProvisioningServerUrl(
     std::string* default_url) {
@@ -114,7 +255,11 @@ CdmResponseType CertificateProvisioning::Init(
       service_certificate.empty()
           ? wvutil::a2bs_hex(kCpProductionServiceCertificate)
           : service_certificate;
-  return service_certificate_->Init(certificate);
+  const CdmResponseType result = service_certificate_->Init(certificate);
+  if (result == NO_ERROR) {
+    state_ = kInitialized;
+  }
+  return result;
 }
 
 // Fill in the appropriate SPOID (Stable Per-Origin IDentifier) option.
@@ -206,11 +351,18 @@ CdmResponseType CertificateProvisioning::GetProvisioningRequestInternal(
 
   default_url->assign(kProvisioningServerUrl);
 
+  if (state_ != kInitialized) {
+    LOGD("Overriding old request: state = %s", StateToString(state_));
+    // Once the previous session is closed, there is no way to complete
+    // an in-flight request.
+    state_ = kInitialized;
+  }
+
   CloseSession();
   CdmResponseType status = crypto_session_->Open(requested_security_level);
   if (NO_ERROR != status) {
-    LOGE("Failed to create a crypto session: status = %d",
-         static_cast<int>(status));
+    LOGE("Failed to create a crypto session: status = %s",
+         status.ToString().c_str());
     return status;
   }
 
@@ -299,6 +451,7 @@ CdmResponseType CertificateProvisioning::GetProvisioningRequestInternal(
   } else {
     *request = std::move(serialized_request);
   }
+  state_ = kDrmRequestSent;
   return CdmResponseType(NO_ERROR);
 }
 
@@ -324,7 +477,11 @@ CdmResponseType CertificateProvisioning::GetProvisioning40RequestInternal(
     return CdmResponseType(PROVISIONING_4_FAILED_TO_INITIALIZE_DEVICE_FILES);
   }
 
-  ProvisioningRequest provisioning_request;
+  if (!service_certificate_) {
+    LOGE("Service certificate not set");
+    return CdmResponseType(CERT_PROVISIONING_EMPTY_SERVICE_CERTIFICATE);
+  }
+
   // Determine the current stage by checking if OEM cert exists.
   std::string stored_oem_cert;
   if (global_file_handle.HasOemCertificate()) {
@@ -341,9 +498,11 @@ CdmResponseType CertificateProvisioning::GetProvisioning40RequestInternal(
       }
     }
   }
+  const bool is_oem_prov_request = stored_oem_cert.empty();
 
   // Retrieve the Spoid, but put it to the client identification instead, so it
   // is encrypted.
+  ProvisioningRequest provisioning_request;
   CdmAppParameterMap additional_parameter;
   CdmResponseType status =
       SetSpoidParameter(origin, spoid, &provisioning_request);
@@ -363,7 +522,7 @@ CdmResponseType CertificateProvisioning::GetProvisioning40RequestInternal(
     provisioning_request.clear_stable_id();
   }
 
-  if (stored_oem_cert.empty()) {
+  if (is_oem_prov_request) {
     // This is the first stage provisioning.
     default_url->assign(std::string(kProvisioningServerUrl) +
                         kProv40FirstStageServerUrlSuffix);
@@ -377,8 +536,8 @@ CdmResponseType CertificateProvisioning::GetProvisioning40RequestInternal(
 
     // Since |stored_oem_cert| is empty, the client identification token will be
     // retrieved from OEMCrypto, which is the BCC in this case.
-    status = FillEncryptedClientId(stored_oem_cert, provisioning_request,
-                                   wv_service_cert);
+    status = FillEncryptedClientId(/* client_token = */ std::string(),
+                                   provisioning_request, wv_service_cert);
     if (status != NO_ERROR) return status;
   } else {
     // This is the second stage provisioning.
@@ -416,25 +575,24 @@ CdmResponseType CertificateProvisioning::GetProvisioning40RequestInternal(
 
   std::string public_key;
   std::string public_key_signature;
-  provisioning_40_wrapped_private_key_.clear();
-  provisioning_40_key_type_ = CryptoWrappedKey::kUninitialized;
+  std::string wrapped_private_key;
+  CryptoWrappedKey::Type private_key_type = CryptoWrappedKey::kUninitialized;
   status = crypto_session_->GenerateCertificateKeyPair(
-      &public_key, &public_key_signature, &provisioning_40_wrapped_private_key_,
-      &provisioning_40_key_type_);
+      &public_key, &public_key_signature, &wrapped_private_key,
+      &private_key_type);
   if (status != NO_ERROR) return status;
 
   PublicKeyToCertify* key_to_certify =
       provisioning_request.mutable_certificate_public_key();
   key_to_certify->set_public_key(public_key);
   key_to_certify->set_signature(public_key_signature);
-  key_to_certify->set_key_type(provisioning_40_key_type_ ==
-                                       CryptoWrappedKey::kRsa
+  key_to_certify->set_key_type(private_key_type == CryptoWrappedKey::kRsa
                                    ? PublicKeyToCertify::RSA
                                    : PublicKeyToCertify::ECC);
 
   std::string serialized_message;
   provisioning_request.SerializeToString(&serialized_message);
-  provisioning_request_message_ = serialized_message;
+  prov40_request_ = serialized_message;
 
   SignedProvisioningMessage signed_provisioning_msg;
   signed_provisioning_msg.set_message(serialized_message);
@@ -490,6 +648,15 @@ CdmResponseType CertificateProvisioning::GetProvisioning40RequestInternal(
     *request = std::move(serialized_request);
   }
   request_ = std::move(serialized_message);
+  // Need the wrapped Prov 4.0 private key to store once the response
+  // is received.  The wrapped key is not available in the response.
+  prov40_wrapped_private_key_ =
+      CryptoWrappedKey(private_key_type, std::move(wrapped_private_key));
+  // Store the public key from the request.  This is used to match
+  // up the response with the most recently generated request.
+  prov40_public_key_ = std::move(public_key);
+
+  state_ = is_oem_prov_request ? kOemRequestSent : kDrmRequestSent;
   return CdmResponseType(NO_ERROR);
 }
 
@@ -552,6 +719,18 @@ CdmResponseType CertificateProvisioning::HandleProvisioning40Response(
         return CdmResponseType(PROVISIONING_4_RESPONSE_HAS_ERROR_STATUS);
     }
   }
+  if (state_ == kOemResponseReceived || state_ == kDrmResponseReceived) {
+    // A response has already been received (successfully), this
+    // response can be silently dropped.
+    LOGW("Response already received: state = %s", StateToString(state_));
+    return CdmResponseType(NO_ERROR);
+  }
+  if (state_ != kOemRequestSent && state_ != kDrmRequestSent) {
+    LOGE("Not expecting a response: state = %s", StateToString(state_));
+    return CdmResponseType(PROVISIONING_UNEXPECTED_RESPONSE_ERROR);
+  }
+  LOGD("Handling response: state = %s", StateToString(state_));
+  const bool is_oem_prov_response = (state_ == kOemRequestSent);
 
   const std::string& device_certificate =
       provisioning_response.device_certificate();
@@ -560,17 +739,16 @@ CdmResponseType CertificateProvisioning::HandleProvisioning40Response(
     return CdmResponseType(PROVISIONING_4_RESPONSE_HAS_NO_CERTIFICATE);
   }
 
-  if (provisioning_40_wrapped_private_key_.empty()) {
-    LOGE("No private key was generated");
+  if (!prov40_wrapped_private_key_.IsValid() || prov40_public_key_.empty()) {
+    LOGE("No %s key was generated",
+         !prov40_wrapped_private_key_.IsValid() ? "private" : "public");
     return CdmResponseType(PROVISIONING_4_NO_PRIVATE_KEY);
   }
 
-  const CryptoWrappedKey private_key(provisioning_40_key_type_,
-                                     provisioning_40_wrapped_private_key_);
-
   if (cert_type_ == kCertificateX509) {
     // Load csr private key to decrypt session key
-    auto status = crypto_session_->LoadCertificatePrivateKey(private_key);
+    auto status =
+        crypto_session_->LoadCertificatePrivateKey(prov40_wrapped_private_key_);
     if (status != NO_ERROR) {
       LOGE("Failed to load x509 certificate.");
       return status;
@@ -581,9 +759,8 @@ CdmResponseType CertificateProvisioning::HandleProvisioning40Response(
     const std::string& signature = signed_response.signature();
     const std::string& core_message = signed_response.oemcrypto_core_message();
     status = crypto_session_->LoadProvisioningCast(
-        signed_response.session_key(), provisioning_request_message_,
-        response_message, core_message, signature,
-        &cast_cert_private_key.key());
+        signed_response.session_key(), prov40_request_, response_message,
+        core_message, signature, &cast_cert_private_key.key());
     if (status != NO_ERROR) {
       LOGE("Failed to generate wrapped key for cast cert.");
       return status;
@@ -593,11 +770,79 @@ CdmResponseType CertificateProvisioning::HandleProvisioning40Response(
 
     *cert = device_certificate;
     *wrapped_key = cast_cert_private_key.key();
+    state_ = is_oem_prov_response ? kOemResponseReceived : kDrmResponseReceived;
+    prov40_wrapped_private_key_.Clear();
+    prov40_public_key_.clear();
     return CdmResponseType(NO_ERROR);
   }
 
+  // Verify that the response contains the same key as the request.
+  // It is possible that multiple requests were generated, the CDM
+  // can only accept the response from the most recently generated
+  // one.
+  //
+  // Check the first few bytes to determine the type of message.
+  // OEM responses:
+  //    ASN.1 DER encoded ContentInfo (containing an X.509 certificate).
+  // DRM responses:
+  //    Protobuf SignedDrmCertificate
+  if (is_oem_prov_response) {
+    // Here |device_certificate| (haystack) is an X.509 cert chain, and
+    // |prov40_public_key_| (needle) is a SubjectPublicKeyInfo.
+    // The cert chain should contain a byte-for-byte copy of the
+    // public key.
+    // TODO(b/391469176): Use RSA/ECC key loading to detected mismatched
+    // keys.
+    if (!StringContains(/* haystack = */ device_certificate,
+                        /* needle */ prov40_public_key_)) {
+      LOGD("OEM response is stale");
+      return CdmResponseType(PROVISIONING_4_STALE_RESPONSE);
+    }
+  } else {  // Is DRM response
+    video_widevine::SignedDrmCertificate signed_certificate;
+    if (!signed_certificate.ParseFromString(device_certificate)) {
+      // Check if ASN.1 like.
+      if (IsAsn1DerSequenceLike(device_certificate)) {
+        // This might be a late OEM certificate response
+        // generated from before the DRM response was received.
+        LOGD("Received late OEM certificate response");
+        return CdmResponseType(PROVISIONING_4_STALE_RESPONSE);
+      }
+      LOGE("Unable to parse Signed DRM certificate");
+      return CdmResponseType(PROVISIONING_4_FAILED_TO_VERIFY_CERT_KEY);
+    }
+    video_widevine::DrmCertificate drm_certificate;
+    if (!drm_certificate.ParseFromString(
+            signed_certificate.drm_certificate())) {
+      LOGE("Unable to parse DRM certificate");
+      return CdmResponseType(PROVISIONING_4_FAILED_TO_VERIFY_CERT_KEY);
+    }
+    // The sent public key is of the format SubjectPublicKeyInfo;
+    // however, the received format is RSAPublicKey (RSA only) or
+    // SubjectPublicKeyInfo (ECC, and future RSA).
+    // Here |prov40_public_key_| (haystack) is SubjectPublicKeyInfo,
+    // and |drm_certificate.public_key()| (needle) may be
+    // SubjectPublicKeyInfo or RSAPublicKey.
+    // If the DRM cert's public key is in SubjectPublicKeyInfo format
+    // it should be a byte-for-byte copy.  If the DRM cert's public key
+    // is RSAPublicKey format then hopefully a byte-for-byte copy is
+    // found within the SubjectPublicKeyInfo.  Note: SubjectPublicKeyInfo
+    // containing an RSA public key uses RSAPublicKey to store the
+    // key fields.
+    // TODO(b/391469176): Use RSA/ECC key loading to detected mismatched
+    // keys.
+    if (!StringContains(/* haystack = */ prov40_public_key_,
+                        /* needle = */ drm_certificate.public_key())) {
+      // This might be a response from a previously generated DRM
+      // certificate response.
+      LOGD("DRM response is stale");
+      return CdmResponseType(PROVISIONING_4_STALE_RESPONSE);
+    }
+  }
+  // Can clear the |prov40_public_key_| after validating.
+  prov40_public_key_.clear();
+
   const CdmSecurityLevel security_level = crypto_session_->GetSecurityLevel();
-  CloseSession();
   wvutil::FileSystem global_file_system;
   DeviceFiles global_file_handle(&global_file_system);
   if (!global_file_handle.Init(security_level)) {
@@ -607,28 +852,45 @@ CdmResponseType CertificateProvisioning::HandleProvisioning40Response(
 
   // Check the stage of the provisioning by checking if an OEM cert is already
   // stored in the file system.
-  if (!global_file_handle.HasOemCertificate()) {
+  if (is_oem_prov_response) {
+    if (global_file_handle.HasOemCertificate()) {
+      // Possible that concurrent apps were generated provisioning
+      // requests, and this one arrived after an other one.
+      LOGI("CDM has already received an OEM certificate");
+      CloseSession();
+      state_ = kOemResponseReceived;
+      prov40_wrapped_private_key_.Clear();
+      prov40_public_key_.clear();
+      return CdmResponseType(NO_ERROR);
+    }
+
     // No OEM cert already stored => the response is expected to be an OEM cert.
     if (!global_file_handle.StoreOemCertificate(device_certificate,
-                                                private_key)) {
+                                                prov40_wrapped_private_key_)) {
       LOGE("Failed to store provisioning 4 OEM certificate");
       return CdmResponseType(PROVISIONING_4_FAILED_TO_STORE_OEM_CERTIFICATE);
     }
-  } else {
-    // The response is assumed to be an DRM cert.
-    DeviceFiles per_origin_file_handle(file_system);
-    if (!per_origin_file_handle.Init(security_level)) {
-      LOGE("Failed to initialize per-origin DeviceFiles");
-      return CdmResponseType(
-          PROVISIONING_4_FAILED_TO_INITIALIZE_DEVICE_FILES_3);
-    }
-    if (!per_origin_file_handle.StoreCertificate(device_certificate,
-                                                 private_key)) {
-      LOGE("Failed to store provisioning 4 DRM certificate");
-      return CdmResponseType(PROVISIONING_4_FAILED_TO_STORE_DRM_CERTIFICATE);
-    }
+    CloseSession();
+    state_ = kOemResponseReceived;
+    prov40_wrapped_private_key_.Clear();
+    prov40_public_key_.clear();
+    return CdmResponseType(NO_ERROR);
   }
-
+  // The response is assumed to be a DRM cert.
+  DeviceFiles per_origin_file_handle(file_system);
+  if (!per_origin_file_handle.Init(security_level)) {
+    LOGE("Failed to initialize per-origin DeviceFiles");
+    return CdmResponseType(PROVISIONING_4_FAILED_TO_INITIALIZE_DEVICE_FILES_3);
+  }
+  if (!per_origin_file_handle.StoreCertificate(device_certificate,
+                                               prov40_wrapped_private_key_)) {
+    LOGE("Failed to store provisioning 4 DRM certificate");
+    return CdmResponseType(PROVISIONING_4_FAILED_TO_STORE_DRM_CERTIFICATE);
+  }
+  CloseSession();
+  state_ = kDrmResponseReceived;
+  prov40_wrapped_private_key_.Clear();
+  prov40_public_key_.clear();
   return CdmResponseType(NO_ERROR);
 }
 
@@ -678,6 +940,15 @@ CdmResponseType CertificateProvisioning::HandleProvisioningResponse(
                                         wrapped_key);
   }
 
+  if (state_ == kDrmResponseReceived) {
+    LOGD("Response already received");
+    return CdmResponseType(NO_ERROR);
+  }
+  if (state_ != kDrmRequestSent) {
+    LOGE("Not expecting a response: state = %s", StateToString(state_));
+    return CdmResponseType(PROVISIONING_UNEXPECTED_RESPONSE_ERROR);
+  }
+
   bool error = false;
   if (!signed_response.has_signature()) {
     LOGE("Signed response does not have signature");
@@ -753,6 +1024,7 @@ CdmResponseType CertificateProvisioning::HandleProvisioningResponse(
   if (cert_type_ == kCertificateX509) {
     *cert = device_cert_data;
     *wrapped_key = private_key.key();
+    state_ = kDrmResponseReceived;
     return CdmResponseType(NO_ERROR);
   }
 
@@ -799,6 +1071,7 @@ CdmResponseType CertificateProvisioning::HandleProvisioningResponse(
     return CdmResponseType(CERT_PROVISIONING_RESPONSE_ERROR_8);
   }
 
+  state_ = kDrmResponseReceived;
   return CdmResponseType(NO_ERROR);
 }
 
diff --git a/libwvdrmengine/cdm/core/src/device_files.cpp b/libwvdrmengine/cdm/core/src/device_files.cpp
index c3ca252a..efe61c8e 100644
--- a/libwvdrmengine/cdm/core/src/device_files.cpp
+++ b/libwvdrmengine/cdm/core/src/device_files.cpp
@@ -709,17 +709,26 @@ bool DeviceFiles::RemoveCertificate() {
   RETURN_FALSE_IF_UNINITIALIZED()
 
   std::string certificate_file_name;
-  if (GetCertificateFileName(kCertificateLegacy, &certificate_file_name))
-    RemoveFile(certificate_file_name);
-  if (GetCertificateFileName(kCertificateDefault, &certificate_file_name))
-    return RemoveFile(certificate_file_name);
-  return true;
+  // Return true so long as at least one certificate was removed.
+  // This is to compliment the behavior of HasCertificate() which
+  // returns true if at least one certificate exists.
+  bool result = false;
+  if (GetCertificateFileName(kCertificateLegacy, &certificate_file_name)) {
+    LOGI("Removing legacy DRM cert");
+    result |= RemoveFile(certificate_file_name);
+  }
+  if (GetCertificateFileName(kCertificateDefault, &certificate_file_name)) {
+    LOGI("Removing DRM cert");
+    result |= RemoveFile(certificate_file_name);
+  }
+  return result;
 }
 
 bool DeviceFiles::RemoveOemCertificate() {
   RETURN_FALSE_IF_UNINITIALIZED()
   std::string certificate_file_name;
   if (GetOemCertificateFileName(&certificate_file_name)) {
+    LOGI("Removing OEM certificate");
     return RemoveFile(certificate_file_name);
   }
   return true;
diff --git a/libwvdrmengine/cdm/core/src/wv_cdm_types.cpp b/libwvdrmengine/cdm/core/src/wv_cdm_types.cpp
index 28b3969d..73968616 100644
--- a/libwvdrmengine/cdm/core/src/wv_cdm_types.cpp
+++ b/libwvdrmengine/cdm/core/src/wv_cdm_types.cpp
@@ -879,6 +879,12 @@ const char* CdmResponseEnumToString(CdmResponseEnum cdm_response_enum) {
       return "SESSION_NOT_FOUND_GENERIC_CRYPTO";
     case SESSION_NOT_FOUND_24:
       return "SESSION_NOT_FOUND_24";
+    case PROVISIONING_UNEXPECTED_RESPONSE_ERROR:
+      return "PROVISIONING_UNEXPECTED_RESPONSE_ERROR";
+    case PROVISIONING_4_STALE_RESPONSE:
+      return "PROVISIONING_4_STALE_RESPONSE";
+    case PROVISIONING_4_FAILED_TO_VERIFY_CERT_KEY:
+      return "PROVISIONING_4_FAILED_TO_VERIFY_CERT_KEY";
   }
   return UnknownValueRep(cdm_response_enum);
 }
diff --git a/libwvdrmengine/cdm/core/test/certificate_provisioning_unittest.cpp b/libwvdrmengine/cdm/core/test/certificate_provisioning_unittest.cpp
index fcc62117..73ace83a 100644
--- a/libwvdrmengine/cdm/core/test/certificate_provisioning_unittest.cpp
+++ b/libwvdrmengine/cdm/core/test/certificate_provisioning_unittest.cpp
@@ -413,6 +413,9 @@ TEST_P(CertificateProvisioningTest, ProvisioningRequestFailsEmptySignature) {
 TEST_P(CertificateProvisioningTest,
        ProvisioningResponseFailsWithEmptyResponse) {
   certificate_provisioning_->Init("");
+  // Must set state if not generating request.
+  certificate_provisioning_->SetStateForTesting(
+      CertificateProvisioning::kDrmRequestSent);
 
   MockFileSystem file_system;
   std::string certificate;
@@ -425,6 +428,9 @@ TEST_P(CertificateProvisioningTest,
 TEST_P(CertificateProvisioningTest,
        ProvisioningResponseFailsIfDeviceIsRevoked) {
   certificate_provisioning_->Init("");
+  // Must set state if not generating request.
+  certificate_provisioning_->SetStateForTesting(
+      CertificateProvisioning::kDrmRequestSent);
 
   MockFileSystem file_system;
   std::string response_certificate;
@@ -445,6 +451,10 @@ TEST_P(CertificateProvisioningTest,
 
 TEST_P(CertificateProvisioningTest, ProvisioningResponseSuccess) {
   certificate_provisioning_->Init("");
+  // Must set state if not generating request.
+  certificate_provisioning_->SetStateForTesting(
+      CertificateProvisioning::kDrmRequestSent);
+
   std::string expected_certificate;
   std::string response;
   ASSERT_TRUE(MakeSignedDrmCertificate(kFakePublicKey, kSerialNumber, kSystemId,
diff --git a/libwvdrmengine/cdm/core/test/core_integration_test.cpp b/libwvdrmengine/cdm/core/test/core_integration_test.cpp
index 03bd37f2..f1a3b1b1 100644
--- a/libwvdrmengine/cdm/core/test/core_integration_test.cpp
+++ b/libwvdrmengine/cdm/core/test/core_integration_test.cpp
@@ -279,4 +279,539 @@ TEST_F(CoreIntegrationTest, NeedKeyBeforeLicenseLoad) {
   EXPECT_EQ(NEED_KEY, holder.Decrypt(key_id));
   ASSERT_NO_FATAL_FAILURE(holder.CloseSession());
 }
+
+class Prov40IntegrationTest : public WvCdmTestBaseWithEngine {
+ public:
+  void SetUp() override {
+    WvCdmTestBaseWithEngine::SetUp();
+    // Ensure CDM is operating using Provisioning 4.0.
+    std::string prov_model;
+    CdmResponseType status = cdm_engine_.QueryStatus(
+        kLevelDefault, QUERY_KEY_PROVISIONING_MODEL, &prov_model);
+    ASSERT_EQ(status, NO_ERROR) << "Failed to determine provisioning model";
+    if (prov_model != QUERY_VALUE_BOOT_CERTIFICATE_CHAIN) {
+      GTEST_SKIP() << "Test is for Prov4.0 only";
+      return;
+    }
+    // Ensure CDM is not provisioned.
+    if (IsProvisioned()) {
+      status = cdm_engine_.Unprovision(kSecurityLevelL1);
+      ASSERT_EQ(status, NO_ERROR) << "Failed to unprovision DRM cert";
+      status = cdm_engine_.UnprovisionOemCert(kSecurityLevelL1);
+      ASSERT_EQ(status, NO_ERROR) << "Failed to unprovision OEM cert";
+      ASSERT_EQ(GetProvisioningStatus(), kNeedsOemCertProvisioning);
+    }
+  }
+
+  CdmProvisioningStatus GetProvisioningStatus() {
+    return cdm_engine_.GetProvisioningStatus(kSecurityLevelL1);
+  }
+
+  bool IsProvisioned() { return cdm_engine_.IsProvisioned(kSecurityLevelL1); }
+
+  void PreDrmProvisioningCheck() {
+    ASSERT_EQ(GetProvisioningStatus(), kNeedsOemCertProvisioning)
+        << "Not in valid state for pre DRM provisioning check";
+    ProvisioningHolder provisioner(&cdm_engine_, config_);
+    // OEM provisioning.
+    ASSERT_NO_FATAL_FAILURE(provisioner.Provision(binary_provisioning_))
+        << "OEM Certificate provisioning attempt failed";
+    ASSERT_EQ(GetProvisioningStatus(), kNeedsDrmCertProvisioning)
+        << "OEM Certificate provisioning was not completed";
+  }
+
+  void PostIncompleteOemProvisioningCheck() {
+    ASSERT_EQ(GetProvisioningStatus(), kNeedsOemCertProvisioning)
+        << "Not in valid state for post incomplete OEM provisioning check";
+    ProvisioningHolder provisioner(&cdm_engine_, config_);
+    // OEM provisioning.
+    ASSERT_NO_FATAL_FAILURE(provisioner.Provision(binary_provisioning_))
+        << "OEM Certificate provisioning attempt failed";
+    ASSERT_EQ(GetProvisioningStatus(), kNeedsDrmCertProvisioning)
+        << "OEM Certificate provisioning was not completed";
+    // DRM provisioning.
+    ASSERT_NO_FATAL_FAILURE(provisioner.Provision(binary_provisioning_))
+        << "DRM Certificate provisioning attempt failed";
+    ASSERT_EQ(GetProvisioningStatus(), kProvisioned)
+        << "DRM Certificate provisioning was not completed";
+    // Remaining is the same as post DRM provisioning.
+    ASSERT_NO_FATAL_FAILURE(PostDrmProvisioningCheck())
+        << "Failed post incomplete OEM provisioning check after DRM "
+           "provisioning";
+  }
+
+  void PostOemProvisioningCheck() {
+    ASSERT_EQ(GetProvisioningStatus(), kNeedsDrmCertProvisioning)
+        << "Not in valid state for post OEM provisioning check";
+    ProvisioningHolder provisioner(&cdm_engine_, config_);
+    ASSERT_NO_FATAL_FAILURE(provisioner.Provision(binary_provisioning_))
+        << "DRM Certificate provisioning failed";
+    ASSERT_EQ(GetProvisioningStatus(), kProvisioned)
+        << "DRM Certificate provisioning was not completed";
+    // Remaining is the same as post DRM provisioning.
+    ASSERT_NO_FATAL_FAILURE(PostDrmProvisioningCheck())
+        << "Failed post OEM provisioning check after DRM provisioning";
+  }
+
+  void PostIncompleteDrmProvisioningCheck() {
+    ASSERT_EQ(GetProvisioningStatus(), kNeedsDrmCertProvisioning)
+        << "Not in valid state for post incomplete DRM provisioning check";
+    ProvisioningHolder provisioner(&cdm_engine_, config_);
+    ASSERT_NO_FATAL_FAILURE(provisioner.Provision(binary_provisioning_))
+        << "DRM Certificate provisioning failed";
+    ASSERT_EQ(GetProvisioningStatus(), kProvisioned)
+        << "DRM Certificate provisioning was not completed";
+    // Remaining is the same as post DRM provisioning.
+    ASSERT_NO_FATAL_FAILURE(PostDrmProvisioningCheck())
+        << "Failed post incomplete DRM provisioning check after DRM "
+           "provisioning";
+  }
+
+  void PostDrmProvisioningCheck() {
+    ASSERT_EQ(GetProvisioningStatus(), kProvisioned)
+        << "Not in valid state for post DRM provisioning check";
+    LicenseHolder holder("CDM_Streaming", &cdm_engine_, config_);
+    ASSERT_NO_FATAL_FAILURE(holder.OpenSession());
+    ASSERT_NO_FATAL_FAILURE(holder.FetchLicense());
+    ASSERT_NO_FATAL_FAILURE(holder.LoadLicense());
+    ASSERT_NO_FATAL_FAILURE(holder.CloseSession());
+  }
+};  // class Prov40IntegrationTest
+
+// Expected flow of an app; 1 OEM request-response, 1 DRM request-response.
+//
+// Case: OemReq1, OemResp1, DrmReq1, DrmResp1
+//
+// Notes:
+//    This is Widevine's expected behavior by an app.
+//
+// Post-Case: Load license
+TEST_F(Prov40IntegrationTest, UsualOrder_LoadOem1_LoadDrm1) {
+  ProvisioningHolder provisioner(&cdm_engine_, config_);
+
+  ASSERT_EQ(GetProvisioningStatus(), kNeedsOemCertProvisioning);
+
+  // Round 1 - OEM provisioning (OemReq1, OemResp1).
+  ASSERT_NO_FATAL_FAILURE(provisioner.Provision(binary_provisioning_))
+      << "OEM Certificate provisioning failed";
+  ASSERT_EQ(GetProvisioningStatus(), kNeedsDrmCertProvisioning);
+
+  // Round 2 - DRM provisioning (DrmReq1, DrmResp1).
+  ASSERT_NO_FATAL_FAILURE(provisioner.Provision(binary_provisioning_))
+      << "DRM Certificate provisioning failed";
+  ASSERT_EQ(GetProvisioningStatus(), kProvisioned);
+
+  ASSERT_NO_FATAL_FAILURE(PostDrmProvisioningCheck());
+}
+
+// Case: OemReq1, OemReq2, OemResp1  (OemResp2 is never acquired)
+// Expectation:
+//    CDM handles OemResp1, but does not complete OEM
+//    provisioning.
+//
+// Notes:
+//    This is undesirable behavior by the app, but can be partially
+//    handle by the CDM.
+//    Apps that encounter this situation are likely generating many
+//    provisioning requests and loading them in whatever order they
+//    arrive.
+//
+// Post-Case: OEM provisioning, DRM provisioning, load license
+TEST_F(Prov40IntegrationTest, UnusualOrder_DropOem2_LoadOem1) {
+  ProvisioningHolder provisioner(&cdm_engine_, config_);
+
+  // OEM provisioning.
+  // Generate first request (OemReq1).
+  ASSERT_NO_FATAL_FAILURE(provisioner.GenerateRequest(binary_provisioning_));
+  const std::string oem_request1 = provisioner.request();
+
+  // Generate second request (OemReq2).
+  ASSERT_NO_FATAL_FAILURE(provisioner.GenerateRequest(binary_provisioning_));
+  // Never send for the second request.
+
+  // Use first request for fetching/loading response (OemResp1).
+  // CDM may or may not return an error, but OEM provisioning is still
+  // needed.
+  provisioner.set_request(oem_request1);
+  ASSERT_NO_FATAL_FAILURE(provisioner.FetchResponse());
+  // Do not enforce any particular error (including NO_ERROR).
+  provisioner.LoadResponseReturnStatus(binary_provisioning_);
+  ASSERT_EQ(GetProvisioningStatus(), kNeedsOemCertProvisioning);
+
+  ASSERT_NO_FATAL_FAILURE(PostIncompleteOemProvisioningCheck());
+}
+
+// Case: OemReq1, OemReq2, OemResp2  (OemResp1 is never acquired)
+// Expectation:
+//    CDM handles OemReq2 (NO_ERROR), and OEM provisioning is
+//    completed.
+//
+// Notes:
+//    This is OK behavior by the app.
+//    Only the OEM response from the most recent OEM request will
+//    complete provisioning.
+//
+// Post-Case: OEM provisioning, DRM provisioning, load license
+TEST_F(Prov40IntegrationTest, UnusualOrder_DropOem1_LoadOem2) {
+  ProvisioningHolder provisioner(&cdm_engine_, config_);
+
+  // OEM provisioning.
+  // Generate first request (OemReq1).
+  ASSERT_NO_FATAL_FAILURE(provisioner.GenerateRequest(binary_provisioning_));
+  // Never send for the first request.
+
+  // Generate, fetch and load second request (OemReq2, OemResp2).
+  // This should complete OEM provisioning.
+  ASSERT_NO_FATAL_FAILURE(provisioner.Provision(binary_provisioning_))
+      << "OEM Certificate provisioning failed";
+  ASSERT_EQ(GetProvisioningStatus(), kNeedsDrmCertProvisioning);
+
+  ASSERT_NO_FATAL_FAILURE(PostOemProvisioningCheck());
+}
+
+// Case: OemReq1, OemReq2, OemResp1, OemResp2
+// Expectation:
+//    OemResp1 is handled by the CDM, but does not complete
+//    provisioning.  OemResp2 is accepted by the CDM
+//    and completes provisioning.
+//
+// Notes:
+//    This is undesirable behavior by the app, but can be partially
+//    handle by the CDM.
+//    Only the OEM response from the most recent OEM request will
+//    complete provisioning.
+//
+// Post-Case: DRM provisioning, load license
+TEST_F(Prov40IntegrationTest, UnusualOrder_LoadOem1_LoadOem2) {
+  ProvisioningHolder provisioner(&cdm_engine_, config_);
+
+  // OEM provisioning.
+  // Generate first request, store it for later (OemReq1).
+  ASSERT_NO_FATAL_FAILURE(provisioner.GenerateRequest(binary_provisioning_));
+  const std::string oem_request1 = provisioner.request();
+
+  // Generate second request, store it for later (OemReq2).
+  ASSERT_NO_FATAL_FAILURE(provisioner.GenerateRequest(binary_provisioning_));
+  const std::string oem_request2 = provisioner.request();
+
+  // Use first request for fetching/loading response (OemResp1).
+  // CDM may or may not return an error, but OEM provisioning is still
+  // needed.
+  provisioner.set_request(oem_request1);
+  ASSERT_NO_FATAL_FAILURE(provisioner.FetchResponse());
+  // Do not enforce any particular error (including NO_ERROR).
+  provisioner.LoadResponseReturnStatus(binary_provisioning_);
+  ASSERT_EQ(GetProvisioningStatus(), kNeedsOemCertProvisioning);
+
+  // Use second request for fetching/loading response (OemResp2).
+  // CDM should accept the second response as valid (so long as
+  // a third was not generated).
+  provisioner.set_request(oem_request2);
+  ASSERT_NO_FATAL_FAILURE(provisioner.FetchResponse());
+  ASSERT_NO_FATAL_FAILURE(provisioner.LoadResponse(binary_provisioning_))
+      << "OEM Certificate provisioning failed";
+  ASSERT_EQ(GetProvisioningStatus(), kNeedsDrmCertProvisioning);
+
+  ASSERT_NO_FATAL_FAILURE(PostOemProvisioningCheck());
+}
+
+// Case: OemReq1, OemReq2, OemResp2, OemResp1
+// Expectation:
+//    OemResp2 is accepted by the CDM and comletes OEM provisioning.
+//    OemResp1 does not cause the CDM to be corrupted.
+//
+// Notes:
+//    This is undesirable behavior by the app, cannot be handle
+//    by the CDM.
+//    In single-staged provisioning, the CDM silently drops
+//    any additional provisioning responses; but in two-stage
+//    this cannot easily by determine that the response is a
+//    late OEM response.
+//
+// Post-Case: DRM provisioning, load license
+TEST_F(Prov40IntegrationTest, UnusualOrder_LoadOem2_LoadOem1) {
+  ProvisioningHolder provisioner(&cdm_engine_, config_);
+
+  // OEM provisioning.
+  // Generate first request, store it for later (OemReq1).
+  ASSERT_NO_FATAL_FAILURE(provisioner.GenerateRequest(binary_provisioning_));
+  const std::string oem_request1 = provisioner.request();
+
+  // Generate, fetch and load second request (OemReq2, OemResp2).
+  ASSERT_NO_FATAL_FAILURE(provisioner.Provision(binary_provisioning_))
+      << "OEM Certificate provisioning failed";
+  // Provisioning should be complete.
+  ASSERT_EQ(GetProvisioningStatus(), kNeedsDrmCertProvisioning);
+
+  // Use first request for fetching/loading response (OemResp1).
+  // CDM may or may not return an error, but DRM provisioning
+  // should still be allowed after.
+  provisioner.set_request(oem_request1);
+  ASSERT_NO_FATAL_FAILURE(provisioner.FetchResponse());
+  // Do not enforce any particular error (including NO_ERROR).
+  provisioner.LoadResponseReturnStatus(binary_provisioning_);
+  // Should not effect existing provisioning state.
+  ASSERT_EQ(GetProvisioningStatus(), kNeedsDrmCertProvisioning)
+      << "Late OEM Certificate response invalidated original response";
+
+  ASSERT_NO_FATAL_FAILURE(PostOemProvisioningCheck());
+}
+
+// Case: DrmReq1, DrmReq2, DrmResp1, (DrmResp2 is never acquired)
+// Expectation:
+//    DrmResp1 is handled by the CDM, but does not complete
+//    provisioning.
+//
+// Notes:
+//    This is undesirable behavior by the app, but can be partially
+//    handle by the CDM.
+//    Apps that encounter this situation are likely generating many
+//    provisioning requests and loading them in whatever order they
+//    arrive.
+//    For single-stage, this situation usually returns a signature
+//    failure.
+//
+// Pre-Case: OEM provisioning
+// Post-Case: DRM provisioning, load license
+TEST_F(Prov40IntegrationTest, UnusualOrder_DropDrm2_LoadDrm1) {
+  ASSERT_NO_FATAL_FAILURE(PreDrmProvisioningCheck());
+
+  ProvisioningHolder provisioner(&cdm_engine_, config_);
+  // DRM provisioning.
+  // Generate first request, store it for later (DrmReq1).
+  ASSERT_NO_FATAL_FAILURE(provisioner.GenerateRequest(binary_provisioning_));
+  const std::string drm_request1 = provisioner.request();
+
+  // Generate second request (DrmReq2).
+  ASSERT_NO_FATAL_FAILURE(provisioner.GenerateRequest(binary_provisioning_));
+  // Never send for the second request.
+
+  // Use first request for fetching/loading response (DrmResp1).
+  // CDM may or may not return an error, but DRM provisioning is still
+  // needed.
+  provisioner.set_request(drm_request1);
+  ASSERT_NO_FATAL_FAILURE(provisioner.FetchResponse());
+  // Do not enforce any particular error (including NO_ERROR).
+  provisioner.LoadResponseReturnStatus(binary_provisioning_);
+  ASSERT_EQ(GetProvisioningStatus(), kNeedsDrmCertProvisioning);
+
+  ASSERT_NO_FATAL_FAILURE(PostIncompleteDrmProvisioningCheck());
+}
+
+// Case: DrmReq1, DrmReq2, DrmResp2  (DrmResp1 is never acquired)
+// Expectation:
+//    CDM accepts DrmReq2 (NO_ERROR), and DRM provisioning is
+//    completed.
+//
+// Notes:
+//    This is OK behavior by the app.
+//    Only the DRM response from the most recent DRM request will
+//    complete provisioning.
+//
+// Pre-Case: OEM provisioning
+// Post-Case: Load license
+TEST_F(Prov40IntegrationTest, UnusualOrder_DropDrm1_LoadDrm2) {
+  ASSERT_NO_FATAL_FAILURE(PreDrmProvisioningCheck());
+
+  ProvisioningHolder provisioner(&cdm_engine_, config_);
+  // DRM provisioning.
+  // Generate first request (DrmReq1).
+  ASSERT_NO_FATAL_FAILURE(provisioner.GenerateRequest(binary_provisioning_));
+  // Never send for the first request.
+
+  // Generate, fetch and load second request (DrmReq2, DrmResp2).
+  ASSERT_NO_FATAL_FAILURE(provisioner.Provision(binary_provisioning_))
+      << "DRM Certificate provisioning failed";
+  ASSERT_TRUE(IsProvisioned());
+
+  ASSERT_NO_FATAL_FAILURE(PostDrmProvisioningCheck());
+}
+
+// Case: DrmReq1, DrmReq2, DrmResp1, DrmResp2
+// Expectation:
+//    DrmResp1 is handled by the CDM, but does not complete
+//    provisioning.  DrmResp2 is accepted by the CDM and
+//    completes provisioning.
+//
+// Notes:
+//    This is undesirable behavior by the app, but can be partially
+//    handle by the CDM.
+//    Only the DRM response from the most recent DRM request will
+//    complete provisioning.
+//
+// Pre-Case: OEM provisioning
+// Post-Case: Load license
+TEST_F(Prov40IntegrationTest, UnusualOrder_LoadDrm1_LoadDrm2) {
+  ASSERT_NO_FATAL_FAILURE(PreDrmProvisioningCheck());
+
+  ProvisioningHolder provisioner(&cdm_engine_, config_);
+  // DRM provisioning.
+  // Generate first request, store it for later (DrmReq1).
+  ASSERT_NO_FATAL_FAILURE(provisioner.GenerateRequest(binary_provisioning_));
+  const std::string drm_request1 = provisioner.request();
+
+  // Generate second request, store it for later (DrmReq2).
+  ASSERT_NO_FATAL_FAILURE(provisioner.GenerateRequest(binary_provisioning_));
+  const std::string drm_request2 = provisioner.request();
+
+  // Use first request for fetching/loading response (DrmResp1).
+  // CDM may or may not return an error, but DRM provisioning is still
+  // needed.
+  provisioner.set_request(drm_request1);
+  ASSERT_NO_FATAL_FAILURE(provisioner.FetchResponse());
+  // Do not enforce any particular error (including NO_ERROR).
+  provisioner.LoadResponseReturnStatus(binary_provisioning_);
+  ASSERT_EQ(GetProvisioningStatus(), kNeedsDrmCertProvisioning);
+
+  // Use second request for fetching/loading response (DrmResp2).
+  // CDM should accept the second response as valid (so long as
+  // a third was not generated).
+  provisioner.set_request(drm_request2);
+  ASSERT_NO_FATAL_FAILURE(provisioner.FetchResponse());
+  ASSERT_NO_FATAL_FAILURE(provisioner.LoadResponse(binary_provisioning_))
+      << "DRM Certificate provisioning failed";
+  ASSERT_TRUE(IsProvisioned());
+
+  ASSERT_NO_FATAL_FAILURE(PostDrmProvisioningCheck());
+}
+
+// Case: DrmReq1, DrmReq2, DrmResp2, DrmResp1
+// Expectation:
+//    DrmResp2 is accepted by the CDM (NO_ERROR) and completes
+//    provisioning.  DrmResp1 is handled by the CDM, but is dropped
+//    without causing issues with existing certificates.
+//
+// Notes:
+//    This is undesirable behavior by the app, but can be partially
+//    handle by the CDM.
+//
+// Pre-Case: OEM provisioning
+// Post-Case: Load license
+TEST_F(Prov40IntegrationTest, UnusualOrder_LoadDrm2_LoadDrm1) {
+  ASSERT_NO_FATAL_FAILURE(PreDrmProvisioningCheck());
+
+  ProvisioningHolder provisioner(&cdm_engine_, config_);
+  // DRM provisioning.
+  // Generate first request, store it for later (DrmReq1).
+  ASSERT_NO_FATAL_FAILURE(provisioner.GenerateRequest(binary_provisioning_));
+  const std::string drm_request1 = provisioner.request();
+
+  // Generate, fetch and load second request (DrmReq2, DrmResp2).
+  ASSERT_NO_FATAL_FAILURE(provisioner.Provision(binary_provisioning_))
+      << "DRM Certificate provisioning failed";
+  ASSERT_TRUE(IsProvisioned());
+
+  // Use first request for fetching/loading response (DrmResp1).
+  // CDM may or may not return an error, and the CDM should still
+  // be considered provisioned.
+  provisioner.set_request(drm_request1);
+  ASSERT_NO_FATAL_FAILURE(provisioner.FetchResponse());
+  // Do not enforce any particular error (including NO_ERROR).
+  provisioner.LoadResponseReturnStatus(binary_provisioning_);
+  // Should not effect existing provisioning state.
+  ASSERT_TRUE(IsProvisioned())
+      << "Late DRM Certificate response invalidated original response";
+
+  ASSERT_NO_FATAL_FAILURE(PostDrmProvisioningCheck());
+}
+
+// Case: OemReq1, OemReq2, OemResp2, DrmReq1, OemResp1, DrmResp1
+// Expectation:
+//    OemResp2 will complete OEM provisioning, allowing the
+//    creation of DrmReq1.
+//    OemResp1 (being received after OEM provisioning is completed,
+//    and DRM provisioning initiated) is handled by the CDM
+//    and does not prevent the completion of DRM provisioning.
+//
+//
+// Notes:
+//    This is undesirable behavior by the app, but can be partially
+//    handle by the CDM.
+//    Stale OEM responses should not interrupt DRM provisioning in
+//    progress.
+//
+// Post-Case: Load license
+TEST_F(Prov40IntegrationTest, UnusualOrder_LoadOem2_LoadDrm1_LoadOem1AsDrm) {
+  ProvisioningHolder provisioner(&cdm_engine_, config_);
+
+  // Round 1 - OEM provisioning.
+  // Generated and stored first OEM request (OemReq1)
+  ASSERT_NO_FATAL_FAILURE(provisioner.GenerateRequest(binary_provisioning_));
+  const std::string oem_request1 = provisioner.request();
+
+  // Complete provisioning on the second attempt (OemReq2, OemResp2).
+  ASSERT_NO_FATAL_FAILURE(provisioner.Provision(binary_provisioning_));
+  ASSERT_EQ(GetProvisioningStatus(), kNeedsDrmCertProvisioning);
+
+  // Round 2 - DRM provisioning.
+  // Generate DRM certificate request (DrmReq1).
+  ASSERT_NO_FATAL_FAILURE(provisioner.GenerateRequest(binary_provisioning_));
+  const std::string drm_request1 = provisioner.request();
+
+  // Use OEM request 1 to get an OEM response (OemResp1).
+  // CDM should detect that the OEM response is no longer needed
+  // and should drop the response with or without errors.
+  provisioner.set_request(oem_request1);
+  ASSERT_NO_FATAL_FAILURE(provisioner.FetchResponse());
+  // Do not enforce any particular error (including NO_ERROR).
+  provisioner.LoadResponseReturnStatus(binary_provisioning_);
+  // Should not effect existing provisioning state.
+  ASSERT_EQ(GetProvisioningStatus(), kNeedsDrmCertProvisioning);
+
+  // Use DRM request 1 to get a DRM response (DrmResp1).
+  provisioner.set_request(drm_request1);
+  ASSERT_NO_FATAL_FAILURE(provisioner.FetchResponse());
+  ASSERT_NO_FATAL_FAILURE(provisioner.LoadResponse(binary_provisioning_))
+      << "Real DRM Certificate provisioning failed";
+  ASSERT_TRUE(IsProvisioned());
+
+  ASSERT_NO_FATAL_FAILURE(PostDrmProvisioningCheck());
+}
+
+// Case: OemReq1, OemReq2, OemResp2, DrmReq1, DrmResp1, OemResp1
+// Expectation:
+//    OemResp2 will complete OEM provisioning, allowing the
+//    creation of DrmReq1.
+//    DrmResp1 will complete DRM provisioning.
+//    OemResp1 (being received after OEM provisioning is completed,
+//    and after DRM provisioning is complete) is handled by the CDM
+//    and does not cause any other issue.
+//
+// Notes:
+//    This is undesirable behavior by the app, but can be partially
+//    handle by the CDM.
+//    Any provisioning response received after DRM provisioning
+//    is completed is ignored.
+//
+// Post-Case: Load license
+TEST_F(Prov40IntegrationTest, UnusualOrder_LoadOem2_LoadOem1AsDrm_LoadDrm1) {
+  ProvisioningHolder provisioner(&cdm_engine_, config_);
+
+  // Round 1 - OEM provisioning.
+  // Generated and stored first OEM request (OemReq1)
+  ASSERT_NO_FATAL_FAILURE(provisioner.GenerateRequest(binary_provisioning_));
+  const std::string oem_request1 = provisioner.request();
+
+  // Complete provisioning on the second attempt (OemReq2, OemResp2).
+  ASSERT_NO_FATAL_FAILURE(provisioner.Provision(binary_provisioning_));
+  ASSERT_EQ(GetProvisioningStatus(), kNeedsDrmCertProvisioning);
+
+  // Round 2 - DRM provisioning (DrmReq1, DrmReq2).
+  ASSERT_NO_FATAL_FAILURE(provisioner.Provision(binary_provisioning_));
+  ASSERT_TRUE(IsProvisioned());
+
+  // Use OEM request 1 to get an OEM response (OemResp2).
+  // CDM should detect that CDM is fully provisioned and should drop
+  // the response with or without errors.
+  provisioner.set_request(oem_request1);
+  ASSERT_NO_FATAL_FAILURE(provisioner.FetchResponse());
+  // Do not enforce any particular error (including NO_ERROR).
+  provisioner.LoadResponseReturnStatus(binary_provisioning_);
+  // Should not effect existing provisioning state.
+  ASSERT_TRUE(IsProvisioned())
+      << "Late OEM Certificate response invalidated DRM certificate";
+  ;
+
+  ASSERT_NO_FATAL_FAILURE(PostDrmProvisioningCheck());
+}
 }  // namespace wvcdm
diff --git a/libwvdrmengine/cdm/src/wv_content_decryption_module.cpp b/libwvdrmengine/cdm/src/wv_content_decryption_module.cpp
index b21a075c..11e62770 100644
--- a/libwvdrmengine/cdm/src/wv_content_decryption_module.cpp
+++ b/libwvdrmengine/cdm/src/wv_content_decryption_module.cpp
@@ -346,6 +346,8 @@ CdmResponseType WvContentDecryptionModule::Unprovision(
   // Enable immediate OEMCrypto termination and re-initalization on
   // unprovisioning.
   CryptoSession::DisableDelayedTermination();
+  // Android unprovisioning has historically allowed for both
+  // DRM (app/origin-specific) and OEM (global) unprovisioning.
   return cdm_engine->Unprovision(level);
 }
 
diff --git a/libwvdrmengine/include/mapErrors-inl.h b/libwvdrmengine/include/mapErrors-inl.h
index 05b9fbb8..5f78cecd 100644
--- a/libwvdrmengine/include/mapErrors-inl.h
+++ b/libwvdrmengine/include/mapErrors-inl.h
@@ -270,6 +270,8 @@ static inline WvStatus mapCdmResponseType(wvcdm::CdmResponseType res) {
     case wvcdm::USAGE_INVALID_PARAMETERS_2:
     case wvcdm::USAGE_STORE_ENTRY_RETRIEVE_INVALID_STORAGE_TYPE:
     case wvcdm::CLIENT_TOKEN_NOT_SET:
+    // Stale responses should have been caught by the CDM engine.
+    case wvcdm::PROVISIONING_4_STALE_RESPONSE:
       err = Status::GENERAL_PLUGIN_ERROR;
       break;
     case wvcdm::CLIENT_ID_GENERATE_RANDOM_ERROR:
@@ -299,6 +301,9 @@ static inline WvStatus mapCdmResponseType(wvcdm::CdmResponseType res) {
     case wvcdm::INVALID_QUERY_KEY:
     case wvcdm::KEY_NOT_FOUND_1:
     case wvcdm::SAMPLE_AND_SUBSAMPLE_SIZE_MISMATCH:
+    // Client provided a provisioning response without
+    // generating a provisioning request.
+    case wvcdm::PROVISIONING_UNEXPECTED_RESPONSE_ERROR:
       err = Status::BAD_VALUE;
       break;
     case wvcdm::KEY_NOT_FOUND_3:
@@ -400,6 +405,9 @@ static inline WvStatus mapCdmResponseType(wvcdm::CdmResponseType res) {
     case wvcdm::CERT_PROVISIONING_RESPONSE_ERROR_4:
     case wvcdm::CERT_PROVISIONING_RESPONSE_ERROR_9:
     case wvcdm::LOAD_PROVISIONING_ERROR:
+    // Failure to verify provisioning cert key is always
+    // due to a malformed response.
+    case wvcdm::PROVISIONING_4_FAILED_TO_VERIFY_CERT_KEY:
       err = Status::PROVISIONING_PARSE_ERROR;
       break;
     case wvcdm::CERT_PROVISIONING_RESPONSE_ERROR_10: