ImageMagick 7.0.7-0 Q16 has a NULL Pointer Dereference vulnerability in the function sixel_output_create in coders/sixel.c.
https://usn.ubuntu.com/3681-1/
https://lists.debian.org/debian-lts-announce/2020/09/msg00007.html
https://lists.debian.org/debian-lts-announce/2019/05/msg00015.html