https://github.com/ImageMagick/ImageMagick/issues/1009

diff --git a/coders/webp.c b/coders/webp.c
index fffccd77e937bc66df903de5b869cb38cb777e66..22f662bae40cf48348966475db6d4f7e219704ed 100644 (file)
--- a/coders/webp.c
+++ b/coders/webp.c
@@ -181,6 +181,8 @@ static MagickBooleanType IsWEBPImageLossless(const unsigned char *stream,
   /*
     Read simple header.
   */
+  if (length <= VP8_CHUNK_INDEX)
+    return(MagickFalse);
   if (stream[VP8_CHUNK_INDEX] != EXTENDED_HEADER)
     return(stream[VP8_CHUNK_INDEX] == LOSSLESS_FLAG ? MagickTrue : MagickFalse);
   /*