libavcodec/gifdec.c in FFmpeg before 2.4.2 does not properly compute image heights, which allows remote attackers to cause a denial of service (out-of-bounds access) or possibly have unspecified other impact via crafted GIF data.
http://git.videolan.org/?p=ffmpeg.git%3Ba=commit%3Bh=8f1457864be8fb9653643519dea1c6492f1dde57