diff --git a/libwvdrmengine/cdm/core/src/cdm_engine.cpp b/libwvdrmengine/cdm/core/src/cdm_engine.cpp
index 64457a65..be383e68 100644
--- a/libwvdrmengine/cdm/core/src/cdm_engine.cpp
+++ b/libwvdrmengine/cdm/core/src/cdm_engine.cpp
@@ -1286,6 +1286,7 @@ CdmResponseType CdmEngine::Decrypt(const CdmSessionId& session_id,
     // else we must be level 1 direct and we don't need to return a buffer.
   }
 
+  AutoLock lock(session_list_lock_);
   CdmSessionMap::iterator session_iter = sessions_.end();
   if (session_id.empty()) {
     // Loop through the sessions to find the session containing the key_id
diff --git a/libwvdrmengine/cdm/test/cdm_extended_duration_test.cpp b/libwvdrmengine/cdm/test/cdm_extended_duration_test.cpp
index fad8e394..c8c1b7e2 100644
--- a/libwvdrmengine/cdm/test/cdm_extended_duration_test.cpp
+++ b/libwvdrmengine/cdm/test/cdm_extended_duration_test.cpp
@@ -22,6 +22,7 @@
 #include "string_conversions.h"
 #include "test_base.h"
 #include "url_request.h"
+#include <utils/Thread.h>
 #include "wv_cdm_constants.h"
 #include "wv_content_decryption_module.h"
 
@@ -678,6 +679,43 @@ class WvCdmExtendedDurationTest : public WvCdmTestBase {
     return security_level;
   }
 
+  class CloseSessionThread : public android::Thread {
+   public:
+     CloseSessionThread() :
+         Thread(false),
+         wv_content_decryption_module_(NULL) {}
+     ~CloseSessionThread() {}
+
+     bool Start(WvContentDecryptionModule* decryptor,
+                const CdmSessionId& session_id,
+                uint32_t time_in_msecs) {
+       wv_content_decryption_module_ = decryptor;
+       sess_id_ = session_id;
+       delay_.tv_sec = time_in_msecs / 1000;
+       delay_.tv_nsec = (time_in_msecs % 1000) * 10000000ll;
+       return run("CloseSessionThread") == android::NO_ERROR;
+     }
+
+     void Stop() { requestExitAndWait(); }
+
+   private:
+    virtual bool threadLoop() {
+      struct timespec delay_remaining;
+      int result = nanosleep(&delay_, &delay_remaining);
+      while (result < 0 &&
+                (delay_remaining.tv_sec > 0 || delay_remaining.tv_nsec > 0)) {
+        result = nanosleep(&delay_remaining, &delay_remaining);
+      }
+      wv_content_decryption_module_->CloseSession(sess_id_);
+      return false;
+    }
+
+    WvContentDecryptionModule* wv_content_decryption_module_;
+    CdmSessionId sess_id_;
+    struct timespec delay_;
+    CORE_DISALLOW_COPY_AND_ASSIGN(CloseSessionThread);
+  };
+
   WvContentDecryptionModule decryptor_;
   CdmKeyMessage key_msg_;
   CdmKeyResponse key_response_;
@@ -831,6 +869,74 @@ TEST_F(WvCdmExtendedDurationTest, VerifyLicenseRenewalTest) {
   decryptor_.CloseSession(session_id_);
 }
 
+TEST_F(WvCdmExtendedDurationTest, DecryptionCloseSessionConcurrencyTest) {
+  Unprovision();
+  Provision();
+
+  // Leave session open to avoid CDM termination
+  CdmSessionId session_id;
+  decryptor_.OpenSession(g_key_system, NULL, kDefaultCdmIdentifier, NULL,
+                         &session_id);
+
+  // Retrieve offline license
+  decryptor_.OpenSession(g_key_system, NULL, kDefaultCdmIdentifier, NULL,
+                         &session_id_);
+  GenerateKeyRequest(kOfflineClip2PstInitData, kLicenseTypeOffline);
+  VerifyKeyRequestResponse(g_license_server, g_client_auth, false);
+
+  EXPECT_FALSE(key_set_id_.empty());
+
+  decryptor_.CloseSession(session_id_);
+
+  for (uint32_t j = 0; j < 500; ++j) {
+    decryptor_.OpenSession(g_key_system, NULL, kDefaultCdmIdentifier, NULL,
+                           &session_id_);
+    EXPECT_EQ(KEY_ADDED, decryptor_.RestoreKey(session_id_, key_set_id_));
+
+    CdmResponseType status = NO_ERROR;
+    struct timespec decrypt_delay;
+    decrypt_delay.tv_sec = 0;
+    decrypt_delay.tv_nsec = 10000000ll;  // 10 ms
+
+    CloseSessionThread* thread = new CloseSessionThread();
+    thread->Start(&decryptor_, session_id_, 500 /* 500 ms */);
+    thread = NULL;
+
+    while (status == NO_ERROR) {
+      struct timespec delay_remaining;
+      int result = nanosleep(&decrypt_delay, &delay_remaining);
+      while (result < 0 &&
+                (delay_remaining.tv_sec > 0 || delay_remaining.tv_nsec > 0)) {
+        result = nanosleep(&delay_remaining, &delay_remaining);
+      }
+      SubSampleInfo* data = &kEncryptedOfflineClip2SubSample;
+      for (size_t i = 0; i < data->num_of_subsamples; i++) {
+        std::vector<uint8_t> decrypt_buffer((data + i)->encrypt_data.size());
+        CdmDecryptionParameters decryption_parameters(
+            &(data + i)->key_id, &(data + i)->encrypt_data.front(),
+            (data + i)->encrypt_data.size(), &(data + i)->iv,
+            (data + i)->block_offset, &decrypt_buffer[0]);
+        decryption_parameters.is_encrypted = (data + i)->is_encrypted;
+        decryption_parameters.is_secure = (data + i)->is_secure;
+        decryption_parameters.subsample_flags = (data + i)->subsample_flags;
+        status = decryptor_.Decrypt(session_id_, (data + i)->validate_key_id,
+                                    decryption_parameters);
+
+        switch (status) {
+          case SESSION_NOT_FOUND_FOR_DECRYPT:
+            break;
+          case NO_ERROR:
+            EXPECT_EQ((data + i)->decrypt_data, decrypt_buffer);
+            break;
+          default:
+            EXPECT_TRUE(false);
+        }
+      }
+    }
+  }
+  decryptor_.CloseSession(session_id);
+}
+
 TEST_F(WvCdmExtendedDurationTest, UsageOverflowTest) {
   Provision();
   SubSampleInfo* data = &kEncryptedStreamingClip5SubSample;