dbcve.org
MediawikiCMS

CVE-2022-34750

HIGH · 7.5 CVSS v3.1 Published 2022-06-28
Fix available
A fix is available. Upgrade to after 1.38.1 or later.
See remediation →
84/100
Remediation priority · High
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
An issue was discovered in MediaWiki through 1.38.1. The lemma length of a Wikibase lexeme is currently capped at a thousand characters. Unfortunately, this length is not validated, allowing much larger lexemes to be created, which introduces various denial-of-service attack vectors within the Wikibase and WikibaseLexeme extensions. This is related to Special:NewLexeme and Special:NewProperty.

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

MediaWiki's WikibaseLexeme extension fails to validate the lemma length limit (capped at 1000 characters) on the server side when creating lexemes via Special:NewLexeme. This allows attackers to submit arbitrarily large lexeme data, causing resource exhaustion (memory, CPU, database) and denial of service.

MitigationImplement server-side validation to enforce the 1000-character lemma length limit in the WikibaseLexeme and Wikibase extensions before persisting lexeme data.

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
MediawikiCMS
Affected:<= 1.38.1

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
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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. Check MediaWiki version
    Navigate to Special:Version or run `php maintenance/run.php version` to determine the installed MediaWiki version
    Affected if version is 1.38.1 or lower
  2. Verify WikibaseLexeme extension is installed
    Check the extensions/ directory for the WikibaseLexeme extension folder, or query the extension registry via Special:Version
    Affected if WikibaseLexeme extension is present and loaded
  3. Confirm Wikibase extension is enabled
    Check if the core Wikibase extension is loaded, visible in Special:Version under installed extensions
    Affected if Wikibase extension is enabled (WikibaseLexeme depends on it)
  4. Verify Special:NewLexeme is accessible
    Attempt to access Special:NewLexeme on the wiki or check if the route is registered in the wiki's special pages list
    Affected if the special page is accessible to users (no restrictions)
  5. Check for oversized lemmas in the database
    Query the lexeme table (typically in the wb lexeme tables) for lemma entries exceeding 1000 characters in length
    Affected if any lemma records exceed 1000 characters (indicates exploitation has occurred)

The environment is affected if running MediaWiki version 1.38.1 or lower with the WikibaseLexeme extension enabled and Special:NewLexeme accessible to 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.

dbcve · scoped
Upgrade available Upgrade to a release after 1.38.1
Interim mitigation

Implement server-side validation to enforce the 1000-character lemma length limit in the WikibaseLexeme and Wikibase extensions before persisting lexeme data.

Recommended fix Moderate confidence

MediaWiki 1.38.2 or later (recommended: latest stable 1.38.x or 1.39.x LTS)

  1. 1. Back up your MediaWiki database and files before any upgrade
  2. 2. Check the current MediaWiki version running on your system (usually in includes/Defines.php or Special:Version)
  3. 3. Review the MediaWiki release notes for versions 1.38.2 and later for security fixes related to Wikibase/WikibaseLexeme
  4. 4. Download the latest stable MediaWiki release (1.38.x or 1.39.x LTS) from https://www.mediawiki.org/
  5. 5. Follow the standard MediaWiki upgrade procedure: upload new files, run update.php, clear caches
  6. 6. Verify that the Wikibase Special:NewLexeme and Special:NewProperty pages now properly enforce the 1000-character lemma length limit
  7. 7. Test that legitimate lexeme creation still functions correctly with lengths up to 1000 characters
Caveat MediaWiki upgrades may include database schema changes; backup before upgrading and test in staging first

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

Fix this in Mediawiki Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2022-34750 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2022-34750 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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