The gs_makewordimagedevice function in base/gsdevmem.c in Artifex Software, Inc. Ghostscript 9.20 allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) via a crafted file that is mishandled in the PDF Transparency module.
https://security.gentoo.org/glsa/201708-06
https://euvd.enisa.europa.eu/vulnerability/EUVD-2016-1405
https://bugs.ghostscript.com/show_bug.cgi?id=697450
http://www.ghostscript.com/cgi-bin/findgit.cgi?daf85701dab05f17e924a48a81edc9195b4a04e8