diff --git a/framesequence/jni/FrameSequence_webp.cpp b/framesequence/jni/FrameSequence_webp.cpp
index 602feb7..7ffb350 100644
--- a/framesequence/jni/FrameSequence_webp.cpp
+++ b/framesequence/jni/FrameSequence_webp.cpp
@@ -84,14 +84,21 @@
 #endif
 }
 
-FrameSequence_webp::FrameSequence_webp(Stream* stream) {
+FrameSequence_webp::FrameSequence_webp(Stream* stream)
+        : mDemux(NULL)
+        , mIsKeyFrame(NULL) {
     // Read RIFF header to get file size.
     uint8_t riff_header[RIFF_HEADER_SIZE];
     if (stream->read(riff_header, RIFF_HEADER_SIZE) != RIFF_HEADER_SIZE) {
         ALOGE("WebP header load failed");
         return;
     }
-    mData.size = CHUNK_HEADER_SIZE + GetLE32(riff_header + TAG_SIZE);
+    uint32_t readSize = GetLE32(riff_header + TAG_SIZE);
+    if (readSize > MAX_CHUNK_PAYLOAD) {
+        ALOGE("WebP got header size too large");
+        return;
+    }
+    mData.size = CHUNK_HEADER_SIZE + readSize;
     mData.bytes = new uint8_t[mData.size];
     memcpy((void*)mData.bytes, riff_header, RIFF_HEADER_SIZE);
 
diff --git a/framesequence/jni/FrameSequence_webp.h b/framesequence/jni/FrameSequence_webp.h
index f4fbec0..111101b 100644
--- a/framesequence/jni/FrameSequence_webp.h
+++ b/framesequence/jni/FrameSequence_webp.h
@@ -32,10 +32,16 @@
     virtual ~FrameSequence_webp();
 
     virtual int getWidth() const {
+        if (!mDemux) {
+            return 0;
+        }
         return WebPDemuxGetI(mDemux, WEBP_FF_CANVAS_WIDTH);
     }
 
     virtual int getHeight() const {
+        if (!mDemux) {
+            return 0;
+        }
         return WebPDemuxGetI(mDemux, WEBP_FF_CANVAS_HEIGHT);
     }
 
@@ -44,6 +50,9 @@
     }
 
     virtual int getFrameCount() const {
+        if (!mDemux) {
+            return 0;
+        }
         return WebPDemuxGetI(mDemux, WEBP_FF_FRAME_COUNT);
     }