The read_header function in libavcodec/ffv1dec.c in FFmpeg before 2.1 does not prevent changes to global parameters, which allows remote attackers to cause a denial of service (out-of-bounds array access) or possibly have unspecified other impact via crafted FFV1 data.
http://openwall.com/lists/oss-security/2013/11/26/7
http://openwall.com/lists/oss-security/2013/12/08/3
https://github.com/FFmpeg/FFmpeg/commit/547d690d676064069d44703a1917e0dab7e33445