The update_dimensions function in libavcodec/vp8.c in FFmpeg through 2.8.1, as used in Google Chrome before 46.0.2490.71 and other products, relies on a coefficient-partition count during multi-threaded operation, which allows remote attackers to cause a denial of service (race condition and memory corruption) or possibly have unspecified other impact via a crafted WebM file.
https://security.gentoo.org/glsa/201603-09
https://lists.debian.org/debian-lts-announce/2018/12/msg00009.html
https://codereview.chromium.org/1376913003
https://code.google.com/p/chromium/issues/detail?id=532967
https://code.google.com/p/chromium/issues/detail?id=447860
http://www.ubuntu.com/usn/USN-2770-2
http://www.ubuntu.com/usn/USN-2770-1
http://www.securitytracker.com/id/1033816
http://www.securityfocus.com/bid/77073
http://www.debian.org/security/2015/dsa-3376
http://rhn.redhat.com/errata/RHSA-2015-1912.html
http://googlechromereleases.blogspot.com/2015/10/stable-channel-update.html
http://git.videolan.org/?p=ffmpeg.git%3Ba=commit%3Bh=dabea74d0e82ea80cd344f630497cafcb3ef872c