In ImageMagick 7.0.7-16 Q16 x86_64 2017-12-22, an infinite loop vulnerability was found in the function ReadTXTImage in coders/txt.c, which allows attackers to cause a denial of service (CPU exhaustion) via a crafted image file that is mishandled in a GetImageIndexInList call.
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
https://lists.debian.org/debian-lts-announce/2018/05/msg00012.html