In Artifex Ghostscript 9.23 before 2018-08-24, a type confusion using the .shfill operator could be used by attackers able to supply crafted PostScript files to crash the interpreter or potentially execute code.
https://www.kb.cert.org/vuls/id/332928
https://usn.ubuntu.com/3768-1/
https://support.f5.com/csp/article/K24803507?utm_source=f5support&%3Butm_medium=RSS
https://security.gentoo.org/glsa/201811-12
https://lists.debian.org/debian-lts-announce/2018/09/msg00015.html
https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44101
https://access.redhat.com/errata/RHSA-2018:3650
http://www.securityfocus.com/bid/105178
http://git.ghostscript.com/?p=ghostpdl.git%3Ba=commit%3Bh=e01e77a36cbb2e0277bc3a63852244bec41be0f6
http://git.ghostscript.com/?p=ghostpdl.git%3Ba=commit%3Bh=0b6cd1918e1ec4ffd087400a754a845180a4522b