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Out-of-bounds ReadWeakness · CWE-125

CVE-2026-34003

HIGH · 7.8 CVSS v3.1 Published 2026-04-23
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
80/100
Remediation priority · High
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.Org X server's XKB key types request validation. A local attacker could send a specially crafted request to the X server, leading to an out-of-bounds memory access vulnerability. This could result in the disclosure of sensitive information or cause the server to crash, leading to a Denial of Service (DoS). In certain configurations, higher impact outcomes may be possible.

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 exists in the X.Org X server's XKB (X Keyboard Extension) key types request validation. A local attacker can send a specially crafted XKB request that triggers an out-of-bounds memory access, potentially leaking sensitive information from memory or causing the X server to crash.

MitigationApply the vendor patch for CVE-2026-34003 to the X.Org X server and restrict local access to the X server to trusted users only.

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
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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. Identify if X.Org X server is installed
    Run 'dpkg -l | grep -i xserver' (Debian/Ubuntu) or 'rpm -qa | grep -i xorg-x11-server' (RHEL/CentOS) or check your system's package manager for xorg-x11-server packages
    Affected if No X server package is found, meaning the system does not use X.Org X server and is not affected
  2. Determine the installed X server version
    Run 'X -version' or 'Xorg -version' to display the X server version number, or query via package manager (e.g., 'dpkg -s xorg-x11-server-core')
    Affected if The installed version is an unpatched X.Org X server version that predates the CVE-2026-34003 fix; compare against vendor security advisories for the patched version number
  3. Verify the XKB extension is loaded
    Run 'xdpyinfo' (if X is running) or check X server log files in /var/log/Xorg.0.log for lines containing 'XKB' to confirm the X Keyboard Extension is active
    Affected if XKB extension is loaded and the X server version is unpatched, making the vulnerability exploitable
  4. Check if the X server is accessible to untrusted users
    Review X server configuration in /etc/X11/xorg.conf or /etc/X11/xorg.conf.d/ for 'DisableTCP' or 'allowed_users' settings, and check X socket permissions in /tmp/.X11-unix/
    Affected if X server allows connections from untrusted local users without authentication (e.g., xhost + or misconfigured xdmcp), increasing exposure to local exploitation

You are affected if an unpatched version of X.Org X server is installed with the XKB extension enabled and accessible to untrusted local users.

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 patch for CVE-2026-34003 to the X.Org X server and restrict local access to the X server to trusted users only.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
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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-2026-34003 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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