An issue was discovered in GraphicsMagick 1.3.26. A NULL pointer dereference vulnerability was found in the function ReadEnhMetaFile in coders/emf.c, which allows attackers to cause a denial of service via a crafted file.
https://www.debian.org/security/2018/dsa-4321
https://usn.ubuntu.com/4266-1/
https://sourceforge.net/p/graphicsmagick/bugs/475/
https://lists.debian.org/debian-lts-announce/2018/08/msg00002.html
https://lists.debian.org/debian-lts-announce/2018/03/msg00025.html
http://hg.graphicsmagick.org/hg/GraphicsMagick/rev/ea074081678b