dbcve.org
FedoraOperating system · Fedoraproject

CVE-2021-45474

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, the Special:ImportFile URI (aka FileImporter) allows XSS, as demonstrated by the clientUrl parameter.

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

Cross-site scripting (XSS) vulnerability in MediaWiki's FileImporter extension (Special:ImportFile) allows injection of malicious JavaScript through the clientUrl parameter. The vulnerable parameter is not properly sanitized before being output in the web page.

MitigationUpgrade MediaWiki to version 1.37.1 or later, or apply the security patch that implements proper output encoding for the clientUrl parameter in the FileImporter extension.

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 inspect LocalSettings.php for the $wgVersion variable to determine the installed MediaWiki version
    Affected if Version is 1.37 or lower
  2. Confirm FileImporter extension is enabled
    Check LocalSettings.php for the require_once or wfLoadExtension call for FileImporter, or look for FileImporter in Special:Version under installed extensions
    Affected if FileImporter extension is loaded and appears in the extensions list
  3. Verify Special:ImportFile is accessible
    Navigate to Special:ImportFile (or index.php?title=Special:ImportFile) in the wiki to confirm the FileImporter special page is accessible
    Affected if The special page loads without permission errors
  4. Inspect clientUrl parameter handling
    Submit a test request to Special:ImportFile with a crafted clientUrl parameter (such as clientUrl=javascript:alert(1)) and verify whether the value is reflected in the page output without proper encoding
    Affected if The clientUrl parameter value is reflected in the HTML output unescaped

A user is affected if they are running MediaWiki version 1.37 or lower with the FileImporter extension enabled and the Special:ImportFile page accessible, where the clientUrl parameter is not properly output-encoded.

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, or apply the security patch that implements proper output encoding for the clientUrl parameter in the FileImporter extension.

Recommended fix Moderate confidence

MediaWiki 1.38 or later (if using Fedora, upgrade to a version that ships MediaWiki > 1.37)

  1. 1. Back up your MediaWiki installation and database before upgrading
  2. 2. Download MediaWiki version 1.38 or later from the official MediaWiki website or package repository
  3. 3. Replace the existing MediaWiki files with the new version
  4. 4. Run the update.php maintenance script to update the database schema if required
  5. 5. Clear any caches (including parser cache, job queue, and CDN caches if used)
  6. 6. Verify the Special:ImportFile functionality works correctly and that the clientUrl parameter is now properly sanitized

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

Fix this in Fedora Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.

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-2021-45474 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