dbcve.org
Information ExposureWeakness · CWE-200

CVE-2025-49177

MEDIUM · 6.1 CVSS v3.1 Published 2025-06-17
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
63/100
Remediation priority · Elevated
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

The XFIXES extension in X11 servers contains an out-of-bounds read vulnerability in the XFixesSetClientDisconnectMode handler. Due to missing validation of the request length, an authenticated client can send a specially crafted request that causes the server to read and return unintended memory contents from previous requests, leading to information disclosure.

MitigationApply vendor patches for the XFIXES extension to address the missing request length validation. Update to patched X server versions and verify client connectivity functions normally.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
Low

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify if X11 server is running
    Run 'ps aux | grep Xorg' or 'ps aux | grep X' to check for running X server processes. Alternatively, check if $DISPLAY is set and the X server is accessible via 'xdpyinfo'.
    Affected if No X server is running (not affected). If X server is running, continue to next checks.
  2. Determine X server implementation and version
    Query the X server version using 'xdpyinfo' or check the package manager: 'dpkg -l | grep xserver-xorg' (Debian) or 'rpm -qa | grep xorg-x11-server' (RHEL). For X.Org server, also check '/usr/bin/X -version'.
    Affected if Cannot determine version - manual investigation needed. Compare installed version against any vendor advisories for CVE-2025-49177.
  3. Verify XFIXES extension is loaded
    Run 'xdpyinfo -queryExtensions' or use 'xlsatoms' to list loaded extensions. Look for 'XFIXES' in the output. The XFIXES extension must be loaded for the vulnerability to be exploitable.
    Affected if XFIXES extension is NOT listed in queryExtensions output (not affected). If XFIXES is present, continue.
  4. Check XFIXES extension version
    Use 'xprop -root _XFIXES_VERSION' or query via 'xdpyinfo' extension details to determine XFIXES extension version number.
    Affected if Extension version cannot be determined - compare your X server/extension combination against vendor patch status.

You are affected if you are running an X11 server with the XFIXES extension loaded and your X server version has not been patched to address the missing request length validation in XFixesSetClientDisconnectMode (CVE-2025-49177).

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply vendor patches for the XFIXES extension to address the missing request length validation. Update to patched X server versions and verify client connectivity functions normally.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing4.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,900
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-49177 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
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