The xps_true_callback_glyph_name function in xps/xpsttf.c in Artifex Ghostscript GhostXPS 9.21 allows remote attackers to cause a denial of service (Segmentation Violation and application crash) via a crafted file.
https://security.gentoo.org/glsa/201811-12
http://www.securityfocus.com/bid/99988
http://git.ghostscript.com/?p=ghostpdl.git%3Ba=commit%3Bh=c53183d4e7103e87368b7cfa15367a47d559e323