CVE-2021-34557

Name: CVE-2021-34557
Creator: NVD / NIST
Published: 2021-06-10T16:15:08.227+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.6/10EPSS 0.48%

Last modified Jun 17, 2026

CVE-2021-34557 is a medium-severity vulnerability rated 4.6/10 on the CVSS scale. 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. EPSS estimates a 0.48% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

4.6/10

CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

0.48%

37.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-120

Affected Software

Vendor	Product	Versions
Xscreensaver Project	Xscreensaver	5.45
Fedoraproject	Fedora	33

References

http://www.openwall.com/lists/oss-security/2021/06/11/1Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/07/06/2Exploit, Mailing List, Third Party Advisory
https://github.com/QubesOS/qubes-issues/issues/6595Issue Tracking, Third Party Advisory
https://github.com/QubesOS/qubes-secpack/blob/master/QSBs/qsb-068-2021.txtExploit, Third Party Advisory
https://github.com/QubesOS/qubes-xscreensaver/blob/master/0001-Fix-updating-outputs-info.patchPatch, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TC4QB7TRS4GS7LDXQQ4PC6J3LVFJYISV/
https://www.openwall.com/lists/oss-security/2021/06/05/1Exploit, Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/06/11/1Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/07/06/2Exploit, Mailing List, Third Party Advisory
https://github.com/QubesOS/qubes-issues/issues/6595Issue Tracking, Third Party Advisory
https://github.com/QubesOS/qubes-secpack/blob/master/QSBs/qsb-068-2021.txtExploit, Third Party Advisory
https://github.com/QubesOS/qubes-xscreensaver/blob/master/0001-Fix-updating-outputs-info.patchPatch, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TC4QB7TRS4GS7LDXQQ4PC6J3LVFJYISV/
https://www.openwall.com/lists/oss-security/2021/06/05/1Exploit, Mailing List, Third Party Advisory

Timeline

Published: Jun 10, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-34557?

How severe is CVE-2021-34557?

CVE-2021-34557 has a CVSS score of 4.6/10 (MEDIUM severity). The EPSS model estimates a 0.48% probability of exploitation in the next 30 days.

How do I fix CVE-2021-34557?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-34557?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST