The ff_ass_split_override_codes function in libavcodec/ass_split.c in FFmpeg before 1.0.2 allows remote attackers to cause a denial of service (NULL pointer dereference and crash) via a subtitle dialog without text.
https://trac.ffmpeg.org/ticket/2048
http://www.ffmpeg.org/security.html
http://secunia.com/advisories/51964
http://git.videolan.org/?p=ffmpeg.git%3Ba=commitdiff%3Bh=20c121c00747d6c3b0b0f98deeff021171b2ed74