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.
http://openwall.com/lists/oss-security/2017/08/31/2
https://lists.debian.org/debian-lts-announce/2018/08/msg00002.html