Bug 1870231 (CVE-2020-16293)

Summary:	CVE-2020-16293 ghostscript: NULL pointer dereference in compose_group_nonknockout_nonblend_isolated_allmask_common() in base/gxblend.c could result in a DoS
Product:	[Other] Security Response	Reporter:	Michael Kaplan <mkaplan>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED ERRATA	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	amasferr, chazlett, deekej, mosvald, twaugh, zdohnal
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:	ghostscript 9.51	Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2021-05-18 20:35:25 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	1870233, 1872070, 1872071
Bug Blocks:	1870273

Description Michael Kaplan 2020-08-19 15:13:23 UTC

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

Comment 1 Michael Kaplan 2020-08-19 15:14:46 UTC

Created ghostscript tracking bugs for this issue:

Affects: fedora-all [bug 1870233]

Comment 3 Todd Cullum 2020-08-24 23:49:27 UTC

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.

Comment 4 Todd Cullum 2020-08-24 23:50:55 UTC

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.

Comment 6 errata-xmlrpc 2021-05-18 15:37:04 UTC

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

Comment 7 Product Security DevOps Team 2021-05-18 20:35:25 UTC

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