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Heap-based Buffer OverflowWeakness · CWE-122

CVE-2024-21885

HIGH · 7.8 CVSS v3.1 Published 2024-02-28
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 X.Org server. In the XISendDeviceHierarchyEvent function, it is possible to exceed the allocated array length when certain new device IDs are added to the xXIHierarchyInfo struct. This can trigger a heap buffer overflow condition, which may lead to an application crash or remote code execution in SSH X11 forwarding environments.

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

Heap buffer overflow vulnerability in X.Org Server's XISendDeviceHierarchyEvent function where array length bounds are not properly checked when adding device IDs to the xXIHierarchyInfo struct, potentially allowing crash or RCE in SSH X11 forwarding environments.

MitigationApply available X.Org Server security patches; if patches unavailable, disable X11 forwarding in SSH configurations unless operationally required.

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. Verify X.Org Server is installed
    Check for the xorg-server package (rpm -q xorg-server, dpkg -l xorg-server, or which Xorg) or examine running processes (ps aux | grep Xorg)
    Affected if X.Org Server is present on the system
  2. Check X.Org Server version
    Run 'Xorg -version' or 'X -version' to obtain the installed version number, then compare against the vulnerable version range for CVE-2024-21885
    Affected if The installed version falls within the vulnerable version range and has not been patched
  3. Confirm X11 forwarding is enabled in SSH
    Inspect /etc/ssh/sshd_config for 'X11Forwarding yes' or check user-specific ~/.ssh/config, or run 'sshd -T | grep x11forwarding'
    Affected if X11Forwarding is set to yes in any active SSH configuration
  4. Verify X Input extension (XI) is active
    Check if XI is loaded by examining Xorg log files (/var/log/Xorg.0.log) for 'XINPUT: extension XI version' or run 'xinput list'
    Affected if The X Input extension is loaded and active, as this is required for the vulnerable code path to be reached

The system is affected if X.Org Server with an unpatched vulnerable version is installed AND X11 forwarding is enabled in SSH, enabling the XISendDeviceHierarchyEvent function to process device hierarchy events.

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 available X.Org Server security patches; if patches unavailable, disable X11 forwarding in SSH configurations unless operationally required.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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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-2024-21885 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
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