Buffer Overflow vulnerability in FFmpeg 4.2 in the build_diff_map function in libavfilter/vf_fieldmatch.c, which could let a remote malicious user cause a Denial of Service.
https://www.debian.org/security/2021/dsa-4990
https://trac.ffmpeg.org/ticket/8239
https://lists.debian.org/debian-lts-announce/2021/08/msg00018.html
http://git.videolan.org/?p=ffmpeg.git%3Ba=commitdiff%3Bh=ce5274c1385d55892a692998923802023526b765