An issue was discovered in Artifex Ghostscript before 9.25. Incorrect “restoration of privilege” checking when running out of stack during exception handling could be used by attackers able to supply crafted PostScript to execute code using the “pipe” instruction. This is due to an incomplete fix for CVE-2018-16509.
Please refer to the "Mitigation" section of CVE-2018-16509 : <https://access.redhat.com/security/cve/cve-2018-16509>