CVE-2026-39934
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 · uneditedLoop with unreachable exit condition ('infinite loop') vulnerability in The Wikimedia Foundation Mediawiki - GrowthExperiments Extension allows Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions. This issue was remediated only on the `master` branch.
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 · moderate confidenceA loop with an unreachable exit condition (infinite loop) in MediaWiki's GrowthExperiments extension can be exploited to facilitate Time-of-Check to Time-of-Use (TOCTOU) race conditions. This allows an attacker to manipulate timing between a security check and the corresponding operation, potentially bypassing intended access controls or causing denial of service through resource exhaustion.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
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
- Authentication
- X
- User interaction
- None
- Scope
- X
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
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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Verify GrowthExperiments extension is enabledCheck your MediaWiki configuration (LocalSettings.php or similar) for extension loading code such as wfLoadExtension( 'GrowthExperiments' ) or look for the extension in your extensions/ directoryAffected if The GrowthExperiments extension is loaded in MediaWiki
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Identify the installed GrowthExperiments versionLocate the extension.json or composer.json file in your extensions/GrowthExperiments directory and read the version fieldAffected if The installed version matches or falls within vulnerable version ranges for this CVE
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Determine which GrowthExperiments features are activeReview your LocalSettings.php for $wgGEEnable... configuration variables that enable specific GrowthExperiments features (such as mentorship, suggested edits, or newcomer tasks)Affected if Features that trigger the vulnerable code path are enabled in the configuration
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Inspect loop logic in GrowthExperiments codeSearch the extensions/GrowthExperiments directory for while or for loops that contain conditional checks on state that could be subject to race conditions, particularly in files handling user task completion or mentorship assignmentsAffected if The vulnerable loop pattern exists and the code path can be triggered through normal extension use
You are affected if the GrowthExperiments extension is enabled and the vulnerable TOCTOU infinite loop code is present in your installed version, especially when the related feature is active.
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 dataOrganizations using the GrowthExperiments extension should update to the master branch version where the remediation was applied, or apply the specific patch addressing the infinite loop condition to prevent TOCTOU exploitation.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-39934 — 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-2026-39934 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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- 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