In Artifex Ghostscript before 9.26, a carefully crafted PDF file can trigger an extremely long running computation when parsing the file.
git.ghostscript.com/?p=ghostpdl.git%3Ba=commitdiff%3Bh=0a7e5a1c309fa0911b892fa40996a7d55d90bace
www.securityfocus.com/bid/106445
bugs.ghostscript.com/show_bug.cgi?id=699856
bugzilla.redhat.com/show_bug.cgi?id=1655607
lists.debian.org/debian-lts-announce/2018/12/msg00019.html
www.ghostscript.com/doc/9.26/History9.htm