dbcve.org
Enterprise LinuxOperating system · Redhat

CVE-2025-26596

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
A heap overflow flaw was found in X.Org and Xwayland. The computation of the length in XkbSizeKeySyms() differs from what is written in XkbWriteKeySyms(), which may lead to a heap-based buffer overflow.

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

A heap overflow vulnerability exists in X.Org Server and Xwayland where the size calculation function XkbSizeKeySyms() computes a different buffer length than what XkbWriteKeySyms() writes, causing a heap-based buffer overflow when processing keyboard symbol data.

MitigationApply vendor patches for X.Org Server and Xwayland once available; until then, restrict X11 access and avoid running untrusted X clients.

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 'rpm -qa xorg-x11-server' or 'dpkg -l xserver-xorg-core' to find the installed package version
    Affected if Installed version is lower than 21.1.16
  2. Check Xwayland version
    Run 'rpm -qa xwayland' or 'dpkg -l xwayland' to find the installed package version
    Affected if Installed version is lower than 24.1.6
  3. Check Tigervnc version
    Run 'rpm -qa tigervnc' or 'dpkg -l tigervnc-server' to find the installed package version
    Affected if Tigervnc is installed (all versions are affected)
  4. Verify XKB extension is in use
    Check for XKB configuration files in /etc/X11/xkb/ or run 'setxkbmap -print' to see if XKB is active; also check Xorg log for XKB initialization messages
    Affected if The vulnerability triggers when processing keyboard symbol data via XKB - the flaw applies when XKB is enabled and handling keyboard symbols

A user is affected if X.org X Server < 21.1.16, Xwayland < 24.1.6, or any version of Tigervnc is installed and XKB keyboard extension is in use.

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.

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

Apply vendor patches for X.Org Server and Xwayland once available; until then, restrict X11 access and avoid running untrusted X clients.

Recommended fix High confidence

X Server >= 21.1.16; Xwayland >= 24.1.6

  1. Update X Server to version 21.1.16 or later
  2. Update Xwayland to version 24.1.6 or later
  3. For Red Hat Enterprise Linux users, apply the latest security updates via: yum update xorg-x11-server* xwayland
  4. For Tigervnc users, update to a version that includes the fixed X Server/Xwayland components
  5. Verify the update was successful by checking the installed versions: xdpyinfo | grep 'X Server' or xwayland --version

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Enterprise Linux Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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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-2025-26596 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