CVE-2023-2831
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 unescape Markdown strings in a memory-efficient way, allowing an attacker to cause a Denial of Service by sending a message containing a large number of escaped characters.
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 contains a memory-inefficient unescape operation when processing Markdown strings. When a message containing a large number of escaped characters (such as backslashes) is processed, the unescaping operation consumes excessive memory, leading to resource exhaustion and denial of service.
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>= 7.1.0, <= 7.1.9>= 7.8.0, <= 7.8.4>= 7.9.0, <= 7.9.3= 7.10.0CVSS 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 the installed Mattermost server versionLog into the Mattermost System Console and navigate to 'About' > 'Mattermost' to view the version number, or run the command: mattermost versionAffected if The installed version falls within any of these ranges: 7.1.0 through 7.1.9, 7.8.0 through 7.8.4, 7.9.0 through 7.9.3, or exactly 7.10.0
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Confirm Markdown message processing is activeVerify the Mattermost server is actively processing user messages containing Markdown. This is enabled by default for all channels and posts. Check that the server is not in a read-only or archived-only state.Affected if Markdown processing is active, which is the default configuration in Mattermost and cannot be selectively disabled for this attack vector
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Check for indicators of resource exhaustionMonitor server memory usage and process health. On the Mattermost host, check system logs and the mattermost process for out-of-memory events or crashes occurring after large Markdown message ingestion.Affected if The server exhibits high memory consumption, crashes, or service degradation when processing messages with many escaped characters (backslashes)
A user is affected if their Mattermost version is 7.1.0-7.1.9, 7.8.0-7.8.4, 7.9.0-7.9.3, or 7.10.0 and the server processes Markdown messages, which is the default behavior.
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 dataApply the vendor patch or upgrade to a fixed version of Mattermost. Additionally, implement message size limits and rate limiting on message ingestion to mitigate exploitation.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-2831 — 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-2023-2831 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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