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Mattermost ServerApplication · Mattermost

CVE-2023-5333

MEDIUM · 6.5 CVSS v3.1 Published 2023-10-09
Fix available
A fix is available. Upgrade to 7.8.11 / 8.0.3 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 deduplicate input IDs allowing a simple user to cause the application to consume excessive resources and possibly crash by sending a specially crafted request to /api/v4/users/ids with multiple identical IDs.

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 confidence

Mattermost's /api/v4/users/ids endpoint does not deduplicate input IDs before processing, allowing authenticated users to send requests with numerous duplicate ID values. This causes the application to perform redundant database queries or processing operations for each duplicate, leading to excessive CPU and memory consumption that can crash the service.

MitigationApply vendor patch or implement input validation to deduplicate the ID array before processing in the /api/v4/users/ids endpoint handler.

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:< 7.8.11>= 8.0.0, < 8.0.3>= 8.1.0, < 8.1.2

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 under About > Mattermost, or inspect the version file in the Mattermost installation directory
    Affected if The installed version falls within < 7.8.11, >= 8.0.0 < 8.0.3, or >= 8.1.0 < 8.1.2
  2. Verify Mattermost API is accessible
    Confirm the Mattermost server is reachable over network and the API endpoints are exposed (typically port 8000 or 443)
    Affected if The server API is accessible over the network to authenticated users or attackers
  3. Confirm user authentication is enabled for the API
    Check that Mattermost is configured to allow user authentication (local, LDAP, or SAML) and that the /api/v4/users/ids endpoint requires valid credentials
    Affected if Authenticated users can access the /api/v4/users/ids endpoint
  4. Check for duplicate ID handling in API requests
    Review Mattermost logs for patterns of /api/v4/users/ids requests with repeated user IDs, or inspect the endpoint handler code if accessible
    Affected if Requests with duplicate user IDs are being processed without deduplication, causing high resource usage

You are affected if your Mattermost Server version is < 7.8.11, >= 8.0.0 < 8.0.3, or >= 8.1.0 < 8.1.2 and the /api/v4/users/ids endpoint is accessible to authenticated users.

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 7.8.11 / 8.0.3 / 8.1.2 or later
Fixed in 7.8.118.0.38.1.2
Interim mitigation

Apply vendor patch or implement input validation to deduplicate the ID array before processing in the /api/v4/users/ids endpoint handler.

Recommended fix High confidence

Upgrade to Mattermost Server 7.8.11, 8.0.3, 8.1.2, or later (recommend latest stable release such as 8.1.x or newer)

  1. 1. Identify the current Mattermost Server version by checking the system console or running 'mattermost version'
  2. 2. Based on your current version, upgrade to a fixed release: if on 7.x upgrade to 7.8.11 or later; if on 8.0.x upgrade to 8.0.3 or later; if on 8.1.0-8.1.1 upgrade to 8.1.2 or later
  3. 3. For Docker deployments, pull the updated image (e.g., mattermost/mattermost-prod-app:8.1.2 or later)
  4. 4. For package installations, update via your package manager or download the appropriate package from mattermost.com
  5. 5. After upgrade, verify the /api/v4/users/ids endpoint now properly deduplicates input IDs before processing
  6. 6. Test that the application runs normally and monitor for any resource consumption anomalies
Caveat Standard Mattermost minor version upgrade; review release notes for any breaking changes in your current branch before upgrading

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
  • Testing3.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,750
Get the upgrade done

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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-2023-5333 in production — separate from our analysis above.

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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