In ImageMagick 7.0.7-28, there is an infinite loop in the ReadOneMNGImage function of the coders/png.c file. Remote attackers could leverage this vulnerability to cause a denial of service via a crafted mng file.
https://github.com/ImageMagick/ImageMagick/issues/1095
https://lists.debian.org/debian-lts-announce/2020/08/msg00030.html