The sws_init_context function in libswscale/utils.c in FFmpeg before 2.7.2 does not initialize certain pixbuf data structures, which allows remote attackers to cause a denial of service (segmentation violation) or possibly have unspecified other impact via crafted video data.
http://ffmpeg.org/security.html
http://git.videolan.org/?p=ffmpeg.git;a=commit;h=a5d44d5c220e12ca0cb7a4eceb0f74759cb13111
http://www.securitytracker.com/id/1033483
http://www.ubuntu.com/usn/USN-2944-1
https://lists.debian.org/debian-lts-announce/2018/12/msg00010.html