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. References: https://bugs.ghostscript.com/show_bug.cgi?id=701795 https://git.ghostscript.com/?p=ghostpdl.git;a=commit;h=7870f4951bcc6a153f317e3439e14d0e929fd231
Created ghostscript tracking bugs for this issue: Affects: fedora-all [bug 1870233]
Flaw summary: In /base/gxblend.c routines do_compose_group() and do_compose_group16(), the check if (has_mask || maskbuf) should be if (has_mask && maskbuf). Since it is not, it's possible for compose_group_nonknockout_nonblend_isolated_allmask_common() to be called without a mask, and a dereference of memory pointed to by mask_row_ptr causes a crash. An attacker would need to trigger this by supplying a crafted PDF file to be processed by ghostscript.
Mitigation: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
This issue has been addressed in the following products: Red Hat Enterprise Linux 8 Via RHSA-2021:1852 https://access.redhat.com/errata/RHSA-2021:1852
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s): https://access.redhat.com/security/cve/cve-2020-16293