What’s Vulnerable › Vulnerabilities

CVE-2021-34557

• Severity: medium (CVSS 4.6 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-06-10 · updated 2026-06-17
• Weakness: CWE-120

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.

Affected products

• Fedoraproject Fedora: 33
• Xscreensaver Project Xscreensaver: 5.45

References

• http://www.openwall.com/lists/oss-security/2021/06/11/1
• http://www.openwall.com/lists/oss-security/2021/07/06/2
• https://github.com/QubesOS/qubes-issues/issues/6595
• https://github.com/QubesOS/qubes-secpack/blob/master/QSBs/qsb-068-2021.txt
• https://github.com/QubesOS/qubes-xscreensaver/blob/master/0001-Fix-updating-outputs-info.patch
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TC4QB7TRS4GS7LDXQQ4PC6J3LVFJYISV/
• https://www.openwall.com/lists/oss-security/2021/06/05/1
• http://www.openwall.com/lists/oss-security/2021/06/11/1
• http://www.openwall.com/lists/oss-security/2021/07/06/2
• https://github.com/QubesOS/qubes-issues/issues/6595
• https://github.com/QubesOS/qubes-secpack/blob/master/QSBs/qsb-068-2021.txt
• https://github.com/QubesOS/qubes-xscreensaver/blob/master/0001-Fix-updating-outputs-info.patch

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