The .sethalftone5 function in psi/zht2.c in Ghostscript before 9.21 allows remote attackers to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted Postscript document that calls .sethalftone5 with an empty operand stack.
git.ghostscript.com/?p=ghostpdl.git%3Ba=commitdiff%3Bh=f5c7555c303
rhn.redhat.com/errata/RHSA-2017-0013.html
rhn.redhat.com/errata/RHSA-2017-0014.html
www.debian.org/security/2016/dsa-3691
www.openwall.com/lists/oss-security/2016/10/11/5
www.openwall.com/lists/oss-security/2016/10/11/7
www.securityfocus.com/bid/95311
bugs.ghostscript.com/show_bug.cgi?id=697203
bugzilla.redhat.com/show_bug.cgi?id=1383940
ghostscript.com/doc/9.21/History9.htm
security.gentoo.org/glsa/201702-31