Off-by-one error in the DrawImage function in magick/render.c in GraphicsMagick 1.3.26 allows remote attackers to cause a denial of service (DrawDashPolygon heap-based buffer over-read and application crash) via a crafted file.
https://www.debian.org/security/2018/dsa-4321
https://usn.ubuntu.com/4232-1/
https://sourceforge.net/p/graphicsmagick/bugs/448/
https://lists.debian.org/debian-lts-announce/2018/06/msg00009.html
http://hg.code.sf.net/p/graphicsmagick/code/rev/2835184bfb78