There is an invalid free in the MagickFree function in magick/memory.c in GraphicsMagick 1.3.26 that will lead to a remote denial of service attack.
hg.graphicsmagick.org/hg/GraphicsMagick/rev/3db9449e3d6a/
openwall.com/lists/oss-security/2017/08/29/4
www.securityfocus.com/bid/100518
bugs.debian.org/878511
bugzilla.redhat.com/show_bug.cgi?id=1484196
lists.debian.org/debian-lts-announce/2018/08/msg00002.html
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PF62B5PJA2JDUOCKJGUQO3SPL74BEYSV/
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WHIKB4TP6KBJWT2UIPWL5MWMG5QXKGEJ/
usn.ubuntu.com/4222-1/
www.debian.org/security/2018/dsa-4321