Integer underflow in the asfrtp_parse_packet function in libavformat/rtpdec_asf.c in FFmpeg before 0.8.3 allows remote attackers to execute arbitrary code via a crafted ASF packet.
http://technet.microsoft.com/en-us/security/msvr/msvr11-012
http://git.videolan.org/?p=ffmpeg.git%3Ba=shortlog%3Bh=n0.8.3
http://git.videolan.org/?p=ffmpeg.git%3Ba=commit%3Bh=c2a2ad133eb9d42361804a568dee336992349a5e