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. http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2015-6820
