CVE-2023-49809
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 fails to handle a null request body in the /add endpoint, allowing a simple member to send a request with null request body to that endpoint and make it crash. After a few repetitions, the plugin is disabled.
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 confidenceMattermost fails to properly validate request bodies in the /add endpoint. An authenticated simple member can send a null request body to crash the endpoint. Repeated crashes cause the plugin to be automatically disabled.
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<= 8.1.5>= 9.0.0, <= 9.1.0CVSS 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 Mattermost Server versionRun the command: grep -i version /opt/mattermost/version.txt or use the Mattermost system console (Go to System Console > About > Mattermost). Alternatively, check the /api/v4/system/stats endpoint for version information.Affected if The installed version is <= 8.1.5 or >= 9.0.0 and <= 9.1.0
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List installed pluginsNavigate to System Console > Plugin Management, or use the Mattermost API: GET /api/v4/plugins. Review the list of installed plugins that expose HTTP endpoints.Affected if Any plugin is installed that implements an /add REST API endpoint that processes request bodies
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Check plugin API exposureReview the plugin source code or API documentation for any endpoint mapped to /add. If source is unavailable, examine network traffic or plugin logs for requests to patterns like /api/v1/add or /plugins/{plugin_id}/add.Affected if A plugin exposes an /add endpoint that accepts POST/PUT request bodies without validation
You are affected if your Mattermost Server version falls within 8.1.5 or earlier, or between 9.0.0 and 9.1.0 inclusive, AND you have any plugin installed that provides an /add endpoint vulnerable to null body handling.
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 · scopedImplement proper input validation on the /add endpoint to reject null or empty request bodies before processing, and add error handling to prevent denial-of-service via repeated crashes.
Mattermost Server 8.1.6 or later for 8.x releases; Mattermost Server 9.1.1 or later for 9.x releases
- 1. Identify the current Mattermost Server version by checking the system console or running 'mattermost version'.
- 2. If running version <= 8.1.5, upgrade to version 8.1.6 or later.
- 3. If running version >= 9.0.0 and <= 9.1.0, upgrade to version 9.1.1 or later.
- 4. After upgrade, verify the /add endpoint handles null request bodies correctly without crashing.
- 5. Confirm the plugin remains enabled after sending test requests to /add endpoint.
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-49809 — 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-2023-49809 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
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