How severe is CVE-2021-41800?

CVE-2021-41800 has a CVSS score of 5.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-41800?

CVE-2021-41800 affects the following packages: mediawiki/core (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2021-41800?

Update mediawiki/core to 1.36.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-41800 is resolved across your whole dependency graph.

How do I detect CVE-2021-41800 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mediawiki/core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-41800 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2021-41800 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-41800 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-41800?

CVE-2021-41800 has an EPSS (Exploit Prediction Scoring System) score of 1.9%, placing it in the 79th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-41800?

CVE-2021-41800 is classified as CWE-770 (CWE-770). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-41800 published, and has it been updated?

CVE-2021-41800 was published on October 11, 2021 and was last updated on October 20, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘

🐘 Packagist

Not in CISA KEV

MEDIUM severity

CVE-2021-41800 — core

MEDIUMFix: wikimedia/mediawiki@781caf8

CVE-2021-41800 is a medium-severity (CVSS 5.3) CWE-770 vulnerability in mediawiki/core. A fix is available for mediawiki/core — see the affected versions and patch details below.

MediaWiki allows a denial of service

Also known asBIT-mediawiki-2021-41800GHSA-c8wv-qwwc-6j73

Published

Oct 11, 2021

Updated

Oct 20, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.9%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs79th percentile — riskier than 79% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

🐘mediawiki/core

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

MediaWiki before 1.36.2 allows a denial of service (resource consumption because of lengthy query processing time). Visiting Special:Contributions can sometimes result in a long running SQL query because PoolCounter protection is mishandled.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`mediawiki/core`	all versions	1.36.2`composer require mediawiki/core:^1.36.2`

Affected Products

2 products · 4 configurations

fedorafedoraproject

3 versions

333435

Application

mediawikimediawiki

< 1.36.2

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mediawiki/core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update mediawiki/core to 1.36.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-41800 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

O3 Security · Impact-Aware SCA

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