diff --git a/media/libstagefright/MPEG4Extractor.cpp b/media/libstagefright/MPEG4Extractor.cpp
index 27e50d1..6019a85 100644
--- a/media/libstagefright/MPEG4Extractor.cpp
+++ b/media/libstagefright/MPEG4Extractor.cpp
@@ -1409,6 +1409,9 @@
         case FOURCC('s', 't', 'c', 'o'):
         case FOURCC('c', 'o', '6', '4'):
         {
+            if ((mLastTrack == NULL) || (mLastTrack->sampleTable == NULL))
+                return ERROR_MALFORMED;
+
             status_t err =
                 mLastTrack->sampleTable->setChunkOffsetParams(
                         chunk_type, data_offset, chunk_data_size);
@@ -1424,6 +1427,9 @@
 
         case FOURCC('s', 't', 's', 'c'):
         {
+            if ((mLastTrack == NULL) || (mLastTrack->sampleTable == NULL))
+                return ERROR_MALFORMED;
+
             status_t err =
                 mLastTrack->sampleTable->setSampleToChunkParams(
                         data_offset, chunk_data_size);
@@ -1440,6 +1446,9 @@
         case FOURCC('s', 't', 's', 'z'):
         case FOURCC('s', 't', 'z', '2'):
         {
+            if ((mLastTrack == NULL) || (mLastTrack->sampleTable == NULL))
+                return ERROR_MALFORMED;
+
             status_t err =
                 mLastTrack->sampleTable->setSampleSizeParams(
                         chunk_type, data_offset, chunk_data_size);
@@ -1509,6 +1518,9 @@
 
         case FOURCC('s', 't', 't', 's'):
         {
+            if ((mLastTrack == NULL) || (mLastTrack->sampleTable == NULL))
+                return ERROR_MALFORMED;
+
             *offset += chunk_size;
 
             status_t err =
@@ -1524,6 +1536,9 @@
 
         case FOURCC('c', 't', 't', 's'):
         {
+            if ((mLastTrack == NULL) || (mLastTrack->sampleTable == NULL))
+                return ERROR_MALFORMED;
+
             *offset += chunk_size;
 
             status_t err =
@@ -1539,6 +1554,9 @@
 
         case FOURCC('s', 't', 's', 's'):
         {
+            if ((mLastTrack == NULL) || (mLastTrack->sampleTable == NULL))
+                return ERROR_MALFORMED;
+
             *offset += chunk_size;
 
             status_t err =