A null pointer dereference vulnerability in compose_group_nonknockout_nonblend_isolated_allmask_common() in base/gxblend.c of Artifex Software GhostScript v9.50 allows a remote attacker to cause a denial of service via a crafted PDF file. This is fixed in v9.51.
https://www.debian.org/security/2020/dsa-4748
https://usn.ubuntu.com/4469-1/
https://security.gentoo.org/glsa/202008-20
https://lists.debian.org/debian-lts-announce/2020/08/msg00032.html
https://git.ghostscript.com/?p=ghostpdl.git%3Ba=commit%3Bh=7870f4951bcc6a153f317e3439e14d0e929fd231