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Improper LockingWeakness · CWE-667

CVE-2025-49178

MEDIUM · 5.5 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 →
57/100
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 X server's request handling. Non-zero 'bytes to ignore' in a client's request can cause the server to skip processing another client's request, potentially leading to a denial of service.

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

A vulnerability in the X server's request handling logic allows a client with non-zero 'bytes to ignore' in their request to cause the server to skip processing another client's request. This can lead to a denial of service where legitimate clients cannot get their requests serviced.

MitigationApply the vendor-supplied patch to the X server. Until patched, monitor for anomalous X server behavior and consider restricting untrusted clients.

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
None
Integrity
None
Availability
High

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

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. Confirm X server is running
    Identify running X server processes (e.g., Xorg, Xvfb, Xserver) using commands like 'ps aux | grep X' or checking for open ports 6000+ with 'netstat -an | grep -E "600[0-9]|60[0-9]{2}"'
    Affected if Any X server process is running without the vendor patch for CVE-2025-49178
  2. Determine X server version
    Run 'X -version' or 'Xorg -version' to obtain the server version, then compare against any vendor-released patch version for CVE-2025-49178
    Affected if The installed version predates the patched version for this CVE
  3. Monitor for client connection failures
    Review X server logs (typically in /var/log/Xorg.0.log or via 'journalctl -u xorg') for error messages indicating rejected or dropped client requests, especially during periods of heavy client activity
    Affected if Logs show legitimate clients receiving errors or timeouts for request processing
  4. Check for anomalous request patterns
    Use network monitoring (e.g., tcpdump) or X server debugging tools to capture client requests and look for sequences where one client's request with 'extra bytes' appears to correlate with subsequent clients being skipped
    Affected if Analysis reveals patterns of requests being skipped after clients send requests with non-zero padding/ignore bytes

An environment is affected if it runs an unpatched X server version and experiences legitimate client requests being dropped or delayed, especially when multiple clients are sending requests concurrently.

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 the vendor-supplied patch to the X server. Until patched, monitor for anomalous X server behavior and consider restricting untrusted clients.

Have this fixed Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,640
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Scan for this in your stack

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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-2025-49178 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
  • No spam, self-promotion, credentials, or personal data