X-Forwarded-For header allows brute-forcing autoblocked IP addressesGHSA-5vj8-g3qg-4qh6
CRITICALGHSA-5vj8-g3qg-4qh6 is a critical-severity (CVSS 9.8) CWE-444 vulnerability in mediawiki/core. A fix is available for mediawiki/core — see the affected versions and patch details below.
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for GHSA-5vj8-g3qg-4qh6.
EPSS Exploitation Probability
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
mediawiki/core🐘mediawiki/core🐘mediawiki/coreReal-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
An issue was discovered in MediaWiki before 1.35.10, 1.36.x through 1.38.x before 1.38.6, and 1.39.x before 1.39.3. An auto-block can occur for an untrusted X-Forwarded-For header.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | mediawiki/core | ≥ 1.39.0&&< 1.39.3 | 1.39.3composer require mediawiki/core:^1.39.3 |
| 🐘Packagist | mediawiki/core | ≥ 1.38.0&&< 1.38.6 | 1.38.6composer require mediawiki/core:^1.38.6 |
| 🐘Packagist | mediawiki/core | all versions | 1.35.10composer require mediawiki/core:^1.35.10 |
Affected Products
fedorafedoraprojectmediawikimediawikiDetection & mitigation playbook
Open-source dependencyDetect
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 1.39.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-5vj8-g3qg-4qh6 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is GHSA-5vj8-g3qg-4qh6 in your dependencies?
Find it across Packagist, including transitive dependencies.