The ff_sbr_apply function in libavcodec/aacsbr.c in FFmpeg before 2.7.2 does not check for a matching AAC frame syntax element before proceeding with Spectral Band Replication calculations, which allows remote attackers to cause a denial of service (out-of-bounds array access) or possibly have unspecified other impact via crafted AAC data.
https://lists.debian.org/debian-lts-announce/2018/12/msg00009.html
http://www.ubuntu.com/usn/USN-2944-1
http://www.securitytracker.com/id/1033483
http://git.videolan.org/?p=ffmpeg.git%3Ba=commit%3Bh=79a98294da6cd85f8c86b34764c5e0c43b09eea3