libavcodec/on2avc.c in FFmpeg before 2.4.2 does not constrain the number of channels to at most 2, which allows remote attackers to cause a denial of service (out-of-bounds access) or possibly have unspecified other impact via crafted On2 data.
http://git.videolan.org/?p=ffmpeg.git;a=commit;h=550f3e9df3410b3dd975e590042c0d83e20a8da3