CVE-2021-31548
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 · uneditedAn issue was discovered in the AbuseFilter extension for MediaWiki through 1.35.2. A MediaWiki user who is partially blocked or was unsuccessfully blocked could bypass AbuseFilter and have their edits completed.
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 confidenceThe AbuseFilter extension for MediaWiki through 1.35.2 has a bypass vulnerability where users who are partially blocked or were unsuccessfully blocked can have their edits completed without being filtered by AbuseFilter. This allows restricted users to circumvent the abuse detection mechanism.
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<= 1.35.2CVSS 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
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/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 checksWork through these to decide whether this CVE applies to you.
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Check MediaWiki versionAccess Special:Version on your wiki or inspect the includes/Defines.php file for the MW_VERSION constant. Compare the version number to the affected range (<=1.35.2).Affected if The installed MediaWiki version is 1.35.2 or earlier.
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Confirm AbuseFilter extension is installedVerify the AbuseFilter extension directory exists in your /extensions folder and that the extension is loaded in your LocalSettings.php file with 'wfLoadExtension( "AbuseFilter" );' or similar.Affected if The AbuseFilter extension is present and loaded in the wiki configuration.
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Check if partial blocks are in useReview your wiki's block settings in Special:BlockList and Special:Block to identify if any partial (sitewide and page) blocks exist, or if any block attempts have been made.Affected if Partial blocks or block attempts exist on the wiki.
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Verify AbuseFilter is enabled for all edit typesNavigate to Special:AbuseFilter or inspect the abusefilter_filters table in the database to confirm filters are active and set to trigger on all relevant actions.Affected if AbuseFilter rules are active but may not be applied to edits from partially blocked users due to the bypass.
You are affected if running MediaWiki <= 1.35.2 with the AbuseFilter extension enabled, particularly if your wiki uses partial blocks.
Generated from the published advisory. Verify against your own configuration.
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 dataUpgrade MediaWiki and the AbuseFilter extension to a version beyond 1.35.2 that contains the security fix.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
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 locallyCheck whether your project pulls in CVE-2021-31548 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-31548 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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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.
- 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