Bug 1974194 (CVE-2021-34557)

Summary:	CVE-2021-34557 XScreenSaver: buffer overflow in update_screen_layout() allows an attacker to bypass the standard screen lock authentication
Product:	[Other] Security Response	Reporter:	Marian Rehak <mrehak>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED NOTABUG	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	mtasaka
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2021-10-28 05:29:54 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:

Description Marian Rehak 2021-06-21 06:27:51 UTC

XScreenSaver 5.45 can be bypassed if the machine has more than ten disconnectable video outputs. A buffer overflow in update_screen_layout() allows an attacker to bypass the standard screen lock authentication mechanism by crashing XScreenSaver. The attacker must physically disconnect many video outputs.

Reference:

https://github.com/QubesOS/qubes-xscreensaver/blob/master/0001-Fix-updating-outputs-info.patch
https://github.com/QubesOS/qubes-issues/issues/6595
https://github.com/QubesOS/qubes-secpack/blob/master/QSBs/qsb-068-2021.txt
https://www.openwall.com/lists/oss-security/2021/06/05/1
http://www.openwall.com/lists/oss-security/2021/06/11/1

Comment 1 Fedora Update System 2021-08-19 01:10:54 UTC

FEDORA-2021-5af4452ffd has been pushed to the Fedora 33 stable repository.
If problem still persists, please make note of it in this bug report.