The gif_decode_frame function in gifdec.c in libavcodec in FFmpeg before 1.2.1 does not properly manage the disposal methods of frames, which allows remote attackers to cause a denial of service (out-of-bounds array access and application crash) via crafted GIF data.
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.