CVE-2026-9699
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 · uneditedMattermost Plugins versions <=11.6 10.18.11 11.3.6 11.6.5.0 fail to sanitize error responses from the OpenAI API before logging, which allows a user with access to server logs or support packets to obtain a valid or partially reconstructable OpenAI API key via inspection of mattermost.log entries generated during authentication failures. Mattermost Advisory ID: MMSA-2026-00609
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 confidenceMattermost Plugins versions <=11.6, 10.18.11, 11.3.6, and 11.6.5.0 fail to sanitize OpenAI API error responses before writing them to mattermost.log. When authentication failures occur, the raw API error responses including API keys are logged in plain text, allowing users with log file access to extract or partially reconstruct the OpenAI API keys.
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
- High
- User interaction
- None
- Scope
- Changed
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/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.
-
Determine Mattermost Plugins versionAccess the Mattermost System Console > Plugins > Plugin Management, or check the plugins directory for the installed version manifest. Compare against affected versions: <=11.6, 10.18.11, 11.3.6, 11.6.5.0Affected if The installed version matches one of the affected versions or falls within the affected ranges
-
Verify OpenAI plugin is installed and enabledNavigate to System Console > Plugins > Plugin Management and confirm whether the OpenAI plugin (or any plugin using OpenAI API) is installed and enabledAffected if The OpenAI plugin is installed and active in the Mattermost environment
-
Locate the mattermost.log fileThe default location is typically /var/log/mattermost/mattermost.log or within the Mattermost data directory. Check the configuration for the actual log file pathAffected if The log file exists and is accessible for inspection
-
Search logs for plaintext API keysUse grep or a text search to look for patterns resembling 'sk-' (OpenAI API key prefix) in mattermost.log, particularly around timestamps indicating authentication failures or API errors. Example: grep -i 'sk-' /var/log/mattermost/mattermost.logAffected if Plaintext API keys starting with 'sk-' appear in the log file, especially in error messages related to OpenAI authentication failures
You are affected if your Mattermost Plugins version is within the vulnerable range, the OpenAI integration is enabled, and mattermost.log contains plaintext API keys from failed authentication attempts.
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 to the patched version of Mattermost Plugins (>11.6, >10.18.11, >11.3.6, >11.6.5.0) to fix the sanitization issue, and rotate any potentially exposed OpenAI API keys as a precautionary measure.
- 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-2026-9699 — 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-2026-9699 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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