GraphicsMagick 1.3.26 has a denial of service issue in ReadXBMImage() in a coders/xbm.c "Read hex image data" version!=10 case that results in the reader not returning; it would cause large amounts of CPU and memory consumption although the crafted file itself does not request it.
https://www.debian.org/security/2018/dsa-4321
https://usn.ubuntu.com/4222-1/
https://lists.debian.org/debian-lts-announce/2018/08/msg00002.html
http://www.securityfocus.com/bid/100574
http://hg.code.sf.net/p/graphicsmagick/code/rev/233a720bfd5e