dbcve.org
FedoraOperating system · Fedoraproject

CVE-2021-45472

MEDIUM · 6.1 CVSS v3.1 Published 2021-12-24
Fix available
A fix is available. Upgrade to after 1.37 or later.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges

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
In MediaWiki through 1.37, XSS can occur in Wikibase because an external identifier property can have a URL format that includes a $1 formatter substitution marker, and the javascript: URL scheme (among others) can be used.

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

In MediaWiki through 1.37, the Wikibase component allows external identifier properties to define URL formats using $1 formatter substitution markers. The javascript: URL scheme (and similar protocols) are not properly filtered or sanitized when processing these URL formats, allowing attackers to inject malicious JavaScript code that executes in the context of other users' browsers, resulting in reflected cross-site scripting (XSS).

MitigationUpgrade MediaWiki to version 1.37.1 or later which contains the fix, or alternatively implement URL scheme validation/sanitization for external identifier property URL formats in Wikibase to block javascript: and other dangerous protocols.

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
FedoraOperating system
Affected:= 35
MediawikiCMS
Affected:<= 1.37

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
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

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
    Access Special:Version or check includes/Defines.php for $wgVersion, or run `grep 'wgVersion' includes/Defines.php`
    Affected if version is 1.37 or lower
  2. Verify Wikibase extension is enabled
    Check your LocalSettings.php for $wgEnableWikibase or look for 'Wikibase' in Special:Version under installed extensions
    Affected if Wikibase extension is installed and enabled
  3. Identify external identifier properties with URL formats
    Query the database: SELECT * FROM wb_property_info WHERE pi_type = 'url' AND pi_url_format LIKE '%$1%'; or check via Special:Property on the wiki
    Affected if any external identifier properties exist with $1 URL format patterns
  4. Inspect URL format values for dangerous schemes
    Review the URL format values from step 3 for presence of 'javascript:' or other potentially dangerous URL schemes (e.g., data:, vbscript:)
    Affected if URL format patterns contain 'javascript:' or similar executable protocols

You are affected if running MediaWiki 1.37 or lower with Wikibase enabled and external identifier properties configured with URL formats containing javascript: or similar dangerous protocols.

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 1.37
Interim mitigation

Upgrade MediaWiki to version 1.37.1 or later which contains the fix, or alternatively implement URL scheme validation/sanitization for external identifier property URL formats in Wikibase to block javascript: and other dangerous protocols.

Recommended fix Moderate confidence

MediaWiki 1.37.1 or later

  1. Update your MediaWiki installation to version 1.37.1 or later using your distribution's package manager or by downloading from the official MediaWiki release archives
  2. After updating, clear any caches to ensure the new code is loaded
  3. Verify the Wikibase component is updated as part of the MediaWiki update
  4. Test that external identifier properties with URL formats work correctly after the update

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

Fix this in Fedora Scoped from the published advisory
  • Consultation2.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,290
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,664.

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-2021-45472 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