CVE-2025-14822
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 versions 10.11.x <= 10.11.8 fail to validate input size before processing hashtags which allows an authenticated attacker to exhaust CPU resources via a single HTTP request containing a post with thousands space-separated tokens
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 versions 10.11.x through 10.11.8 lack input size validation before processing hashtags in posts. An authenticated attacker can send a single HTTP request containing a post with thousands of space-separated tokens, causing excessive CPU consumption due to inefficient hashtag processing.
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>= 10.11.0, < 10.11.9CVSS 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
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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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Identify installed Mattermost Server versionRun 'mmctl --version' or check the System Console under About > Mattermost, or inspect the Docker/image version tagAffected if The version is 10.11.0 through 10.11.8 inclusive (>=10.11.0 and <10.11.9)
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Confirm post creation is enabled for authenticated usersVerify that the Mattermost instance allows authenticated users to create posts in channels. Check that the 'Allow users to post messages' permission is enabled in System Console > Users and Teams > PermissionsAffected if Authenticated users can create posts in any channel
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Check if rate limiting is configured on post creation endpointsInspect the Mattermost config.json for 'RateLimitSettings' section, or check System Console > Environment > Rate Limit. Verify if rate limiting is enabled and note the settingsAffected if Rate limiting is disabled or set to very high limits on POST /api/v4/posts endpoints
You are affected if your Mattermost Server version is 10.11.0 through 10.11.8 and authenticated users can create posts without sufficient rate limiting protection.
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.
dbcve · scoped10.11.9
Upgrade to Mattermost version 10.11.9 or later which includes proper input validation for hashtag processing. As a temporary mitigation, implement rate limiting on post creation endpoints.
Mattermost Server 10.11.9
- 1. Back up your Mattermost database before upgrading
- 2. Stop the Mattermost Server service
- 3. Download Mattermost Server version 10.11.9 from the official Mattermost downloads page
- 4. Install the upgrade following standard Mattermost upgrade procedures
- 5. Verify the upgrade was successful by checking the server version in the system console
- 6. Restart the Mattermost Server service
- 7. Test that posts with hashtags are processed correctly
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 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 $2,848.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-14822 — 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-2025-14822 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