The Ins_IP function in base/ttinterp.c in Artifex Ghostscript GhostXPS 9.21 allows remote attackers to cause a denial of service (use-after-free and application crash) or possibly have unspecified other impact via a crafted document.
https://security.gentoo.org/glsa/201811-12
http://www.securityfocus.com/bid/99979
http://www.debian.org/security/2017/dsa-3986
http://git.ghostscript.com/?p=ghostpdl.git%3Ba=commit%3Bh=98f6da60b9d463c617e631fc254cf6d66f2e8e3c