Buffer Overflow vulnerability exists in FFmpeg 4.2 in filter_vertically_8 at libavfilter/vf_avgblur.c, which could cause a remote Denial of Service.
https://www.debian.org/security/2021/dsa-4990
https://trac.ffmpeg.org/ticket/8274
https://lists.debian.org/debian-lts-announce/2021/08/msg00018.html