In Artifex Ghostscript through 9.26, ephemeral or transient procedures can allow access to system operators, leading to remote code execution.
https://www.exploit-db.com/exploits/46242/
https://www.debian.org/security/2019/dsa-4372
https://usn.ubuntu.com/3866-1/
https://security.gentoo.org/glsa/202004-03
https://seclists.org/bugtraq/2019/Apr/4
https://lists.debian.org/debian-lts-announce/2019/02/msg00016.html
https://bugs.ghostscript.com/show_bug.cgi?id=700317
https://bugs.chromium.org/p/project-zero/issues/detail?id=1729
https://access.redhat.com/errata/RHSA-2019:0229
https://access.redhat.com/errata/RHBA-2019:0327
http://www.securityfocus.com/bid/106700
http://www.openwall.com/lists/oss-security/2019/03/21/1
http://www.openwall.com/lists/oss-security/2019/01/23/5
http://packetstormsecurity.com/files/152367/Slackware-Security-Advisory-ghostscript-Updates.html
http://packetstormsecurity.com/files/151307/Ghostscript-Pseudo-Operator-Remote-Code-Execution.html
http://lists.opensuse.org/opensuse-security-announce/2019-01/msg00048.html
http://lists.opensuse.org/opensuse-security-announce/2019-01/msg00047.html