dbcve.org
Enterprise LinuxOperating system · Redhat

CVE-2025-26599

HIGH · 7.8 CVSS v3.1 Published 2025-02-25
Fix available
A fix is available. Upgrade to 21.1.16 / 24.1.6 or later.
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
An access to an uninitialized pointer flaw was found in X.Org and Xwayland. The function compCheckRedirect() may fail if it cannot allocate the backing pixmap. In that case, compRedirectWindow() will return a BadAlloc error without validating the window tree marked just before, which leaves the validated data partly initialized and the use of an uninitialized pointer later.

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 uninitialized pointer vulnerability exists in X.Org and Xwayland where compCheckRedirect() fails to properly validate the window tree when a backing pixmap allocation fails. This leaves validated data partly initialized, and an uninitialized pointer is later dereferenced, potentially allowing local privilege escalation or denial of service.

MitigationUpdate X.Org Server and Xwayland to versions containing the fix that properly validates window tree state before returning BadAlloc errors on pixmap allocation failure.

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:= 7.0= 8.0= 9.0
TigervncApplication
Affected:all versions
X ServerApplication
Affected:< 21.1.16
XwaylandApplication
Affected:< 24.1.6

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. Check X.org X Server version
    Run 'Xorg -version' or check your package manager for xorg-x11-server version (e.g., 'rpm -qa | grep xorg-x11-server' or 'dpkg -l | grep xserver-xorg')
    Affected if The installed version is earlier than 21.1.16
  2. Check Xwayland version
    Run 'Xwayland --version' or check your package manager for xwayland package version
    Affected if The installed version is earlier than 24.1.6
  3. Check if Composite extension is enabled
    Examine X server configuration files (xorg.conf, xorg.conf.d/) for 'Composite' extension being loaded, or check running X session with 'xdpyinfo' to see if Composite extension is listed as available
    Affected if Composite extension is enabled and being used (the vulnerable code path in compCheckRedirect() is only triggered when composite window redirection is active)
  4. Check for TigerVNC installation
    Check package manager for tigervnc packages (e.g., 'rpm -qa | grep tigervnc' or 'dpkg -l | grep vnc')
    Affected if TigerVNC is installed (all versions are affected)

You are affected if you are running a vulnerable X.org X Server version before 21.1.16 or Xwayland before 24.1.6, and the Composite extension is enabled and actively redirecting windows.

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
Upgrade available Upgrade to 21.1.16 / 24.1.6 or later
Fixed in 21.1.1624.1.6
Interim mitigation

Update X.Org Server and Xwayland to versions containing the fix that properly validates window tree state before returning BadAlloc errors on pixmap allocation failure.

Fix this in Enterprise Linux Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing8.0 h
  • Review / QA4.0 h
24.0 hours of engineering $4,160
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,656.

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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-2025-26599 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