FFmpeg 0.5 allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via unknown vectors that trigger a stack-based buffer overflow.
scarybeastsecurity.blogspot.com/2009/09/patching-ffmpeg-into-shape.html
secunia.com/advisories/36805
secunia.com/advisories/38643
secunia.com/advisories/39482
www.debian.org/security/2010/dsa-2000
www.securityfocus.com/bid/36465
www.ubuntu.com/usn/USN-931-1
www.vupen.com/english/advisories/2010/0935
roundup.ffmpeg.org/roundup/ffmpeg/issue1240