sp5xdec.c in the Sunplus SP5X JPEG decoder in libavcodec in FFmpeg before 0.6.3 and libav through 0.6.2, as used in VideoLAN VLC media player 1.1.9 and earlier and other products, performs a write operation outside the bounds of an unspecified array, which allows remote attackers to cause a denial of service (memory corruption) or possibly execute arbitrary code via a malformed AMV file.
The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.