GraphicsMagick 1.3.26 has a Memory Leak in the PersistCache function in magick/pixel_cache.c during writing of Magick Persistent Cache (MPC) files.
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://hg.code.sf.net/p/graphicsmagick/code/rev/db732abd9318