dbcve.org
Enterprise LinuxOperating system · Redhat

CVE-2026-34000

CRITICAL · 9.1 CVSS v3.1 Published 2026-05-05
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges 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. This out-of-bounds read vulnerability in the XKB geometry processing, specifically within the `CheckSetGeom()` and `XkbAddGeomKeyAlias` functions, allows an attacker to read uninitialized or out-of-bounds memory. An attacker with a connection to the X11 server, either locally or remotely, can exploit this without user interaction. This could lead to the disclosure of memory contents or cause a denial of service by crashing the server.

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 · high confidence

An out-of-bounds read vulnerability exists in the X.Org X server's XKB (X Keyboard Extension) geometry processing code, specifically in the CheckSetGeom() and XkbAddGeomKeyAlias functions. This flaw allows an attacker with X11 server access to read uninitialized or out-of-bounds memory without user interaction, potentially exposing sensitive memory contents or causing a denial of service via server crash.

MitigationApply the vendor-supplied patch for CVE-2026-34000 to the X.Org X server, ensuring bounds checking is properly implemented in the XKB geometry functions. If no patch is available, consider restricting X11 server access to trusted clients only or disabling the XKB extension if not required.

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

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Enterprise LinuxOperating system
Affected:= 6.0= 7.0= 8.0= 9.0= 10.0
X ServerApplication
Affected:all versions

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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/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. Verify X.Org X server is installed
    Run 'rpm -qa | grep -i xorg-x11-server' on RHEL or 'dpkg -l | grep -i xserver' on Debian-based systems to list installed X server packages
    Affected if No X server package is found, meaning X server is not installed and the system is not affected
  2. Determine installed X server version
    Run 'rpm -q --qf '%{VERSION}-%{RELEASE}' xorg-x11-server-Xorg' (RHEL) or 'dpkg -s xserver-xorg-core' (Debian) to get the exact version number
    Affected if The version matches the affected RHEL versions (6.0, 7.0, 8.0, 9.0, 10.0) or is any version of X.org X Server since all versions are affected
  3. Confirm XKB extension is in use
    Check if XKB is configured by looking for XKB-related configuration files in /etc/X11/xorg.conf.d/ or running 'setxkbmap -print' to test if XKB responds. Also check for XKB options in xorg.conf
    Affected if XKB extension is loaded or configured - the vulnerability exists in XKB geometry processing, so if XKB is not used, the attack surface is reduced
  4. Check if X server is network accessible
    Run 'netstat -tlnp | grep :600' or 'ss -tlnp | grep :600' to see if the X server is listening on TCP ports 6000+
    Affected if The X server is listening on TCP ports (default X11 port 6000), making it network-accessible and vulnerable to remote exploitation

If an X.Org X server is installed (any version) with XKB extension enabled and the server is network-accessible, the environment is vulnerable to CVE-2026-34000.

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 for CVE-2026-34000 to the X.Org X server, ensuring bounds checking is properly implemented in the XKB geometry functions. If no patch is available, consider restricting X11 server access to trusted clients only or disabling the XKB extension if not required.

Fix this in Enterprise Linux Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
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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-2026-34000 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