#VU66593 Buffer overflow in xscreensaver - CVE-2021-34557

Vulnerability identifier: #VU66593

Vulnerability risk: Low

CVSSv4.0: 4 [CVSS:4.0/AV:P/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2021-34557

CWE-ID: CWE-119

Exploitation vector: Local

Exploit availability: No

Vulnerable software:
xscreensaver
Other software / Other software solutions

Vendor: www.jwz.org

Description

The vulnerability allows an attacker to escalate privileges on the system.

The vulnerability exists due to a boundary error within the update_screen_layout()  function. An attacker with physical access to the system can trigger memory corruption and bypass the standard screen lock authentication mechanism.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

xscreensaver: before 5.45-5

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External links
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
https://www.openwall.com/lists/oss-security/2021/06/11/1
https://www.openwall.com/lists/oss-security/2021/07/06/2
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TC4QB7TRS4GS7LDXQQ4PC6J3LVFJYISV/

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Q & A

Can this vulnerability be exploited remotely?

No. The attacker should have physical access to the system in order to successfully exploit this vulnerability.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.