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Mattermost ServerApplication · Mattermost

CVE-2024-24988

MEDIUM · 6.5 CVSS v3.1 Published 2024-02-29
Fix available
A fix is available. Upgrade to 8.1.8 / 9.1.5 or later.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable Zero-click

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 · unedited
Mattermost fails to properly validate the length of the emoji value in the custom user status, allowing an attacker to send multiple times a very long string as an emoji value causing high resource consumption and possibly crashing the server.

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 confidence

Mattermost fails to validate the length of the emoji value in custom user status settings, allowing an attacker to repeatedly submit excessively long strings as emoji values. This unbounded input causes high resource consumption (CPU/memory) through repeated processing of large payloads, potentially leading to server crashes.

MitigationImplement strict length validation for the emoji value field in custom user status, rejecting inputs exceeding a reasonable maximum length (e.g., 64-128 characters), and add rate limiting on status update requests.

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
Mattermost ServerApplication
Affected:< 8.1.8>= 9.0.0, < 9.1.5>= 9.2.0, < 9.2.4

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
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 checks

Work through these to decide whether this CVE applies to you.

  1. Check installed Mattermost Server version
    Run 'mmctl version' or check the Mattermost System Console > About page to find the exact version number
    Affected if The installed version is < 8.1.8, or >= 9.0.0 and < 9.1.5, or >= 9.2.0 and < 9.2.4
  2. Verify custom user status feature is accessible
    Log in as a regular user and navigate to Settings > Custom Status, or check if the custom status API endpoint is available in your environment
    Affected if Users can access custom user status settings without administrative restrictions
  3. Inspect emoji input validation
    Attempt to set a custom status emoji with an extremely long string (e.g., 500+ characters) via the web UI or API POST to /api/v4/users/{user_id}/status/custom
    Affected if The system accepts excessively long emoji values without rejecting them or enforcing a length limit
  4. Monitor server resource consumption
    Review Mattermost server logs and system metrics (CPU, memory) for unusual spikes correlated with custom status update activity
    Affected if Logs show high resource usage or processing delays specifically tied to custom status endpoint requests with large payloads
  5. Check for rate limiting configuration
    Examine Mattermost configuration (config.json) for RateLimit settings under ServiceSettings, particularly related to API endpoints
    Affected if No rate limiting is configured for user status update endpoints, allowing repeated large payload submissions

You are affected if your Mattermost Server version falls within the vulnerable ranges AND users can access custom user status settings without length validation on emoji values.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Upgrade available Upgrade to 8.1.8 / 9.1.5 / 9.2.4 or later
Fixed in 8.1.89.1.59.2.4
Interim mitigation

Implement strict length validation for the emoji value field in custom user status, rejecting inputs exceeding a reasonable maximum length (e.g., 64-128 characters), and add rate limiting on status update requests.

Recommended fix High confidence

Upgrade to 8.1.8 (for 8.x), 9.1.5 (for 9.0-9.1.x), or 9.2.4 (for 9.2.x) depending on your current branch

  1. 1. Identify the current Mattermost Server version by running 'mattermost version' or checking the system console.
  2. 2. For servers running version < 8.1.8: Upgrade to version 8.1.8 or later.
  3. 3. For servers running version 9.0.0 - 9.1.4: Upgrade to version 9.1.5 or later.
  4. 4. For servers running version 9.2.0 - 9.2.3: Upgrade to version 9.2.4 or later.
  5. 5. Before upgrading, backup the database and Mattermost data directory.
  6. 6. Follow the standard Mattermost upgrade procedure: stop the server, install the new version, restart the server.
  7. 7. Verify the upgrade was successful and the server is running properly.
Caveat Check Mattermost release notes for version-specific changes; major version upgrades may include breaking changes

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Mattermost Server Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2024-24988 in production — separate from our analysis above.

No notes yet

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What this is

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.

What belongs here
  • 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