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Mattermost ServerApplication · Mattermost

CVE-2025-12419

CRITICAL · 9.9 CVSS v3.1 Published 2025-11-27
Fix available
A fix is available. Upgrade to 10.5.13 / 10.11.5 or later.
See remediation →
100/100
Remediation priority · Urgent
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 versions 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12, 11.0.x <= 11.0.3 fail to properly validate OAuth state tokens during OpenID Connect authentication which allows an authenticated attacker with team creation privileges to take over a user account via manipulation of authentication data during the OAuth completion flow. This requires email verification to be disabled (default: disabled), OAuth/OpenID Connect to be enabled, and the attacker to control two users in the SSO system with one of them never having logged into Mattermost.

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 fails to properly validate OAuth state tokens during OpenID Connect authentication, allowing an authenticated attacker with team creation privileges to manipulate authentication data during the OAuth completion flow and take over a user account. The attack requires OAuth/OIDC to be enabled, email verification to be disabled, and the attacker to control two SSO users where one has never logged into Mattermost.

MitigationUpgrade to fixed Mattermost versions (10.12.2+, 10.11.5+, 10.5.13+, 11.0.4+) or disable OAuth/OpenID Connect if not required. Enabling email verification provides defense-in-depth.

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:>= 10.5.0, < 10.5.13>= 10.11.0, < 10.11.5>= 10.12.0, < 10.12.2>= 11.0.0, < 11.0.4

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
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/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 Mattermost Server version
    Run 'grep -i version /opt/mattermost/config/config.json' or check the System Console under About > Mattermost. Compare the installed version to the affected ranges: 10.5.0-10.5.12, 10.11.0-10.11.4, 10.12.0-10.12.1, or 11.0.0-11.0.3.
    Affected if Version falls within any of the affected ranges listed.
  2. Verify OAuth/OpenID Connect is enabled
    In System Console, go to Authentication > OpenID SSO (or Authentication > OAuth 2.0) and check if any OAuth provider is enabled (Enable OAuth 2.0 or Enable OpenID Connect is set to true).
    Affected if OAuth, OIDC, or any SSO provider is currently enabled in Mattermost.
  3. Confirm email verification is disabled
    In System Console, go to Authentication > Email and check if 'Enable email verification' is disabled (set to false).
    Affected if Email verification is turned off in the authentication settings.
  4. Check for users with team creation privileges
    In System Console, go to Users > Teams and check if any users have 'Team Creator' role, or verify if default permissions allow authenticated users to create teams (System Console > Site Configuration > Users and Teams).
    Affected if Any authenticated user has team creation privileges, or team creation is allowed for regular users.

You are affected if your Mattermost Server version is in the affected ranges AND OAuth/OIDC is enabled AND email verification is disabled, making the team creation privilege requirement potentially exploitable.

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 10.5.13 / 10.11.5 / 10.12.2 or later
Fixed in 10.5.1310.11.510.12.2
Interim mitigation

Upgrade to fixed Mattermost versions (10.12.2+, 10.11.5+, 10.5.13+, 11.0.4+) or disable OAuth/OpenID Connect if not required. Enabling email verification provides defense-in-depth.

Recommended fix High confidence

Upgrade to Mattermost Server 10.5.13, 10.11.5, 10.12.2, or 11.0.4 (or later) depending on your current major version branch

  1. 1. Identify the current Mattermost Server version by running 'mmctl version' or checking the system console.
  2. 2. Based on the current version, upgrade to the corresponding fixed release: 10.5.13, 10.11.5, 10.12.2, or 11.0.4 (or later).
  3. 3. Back up the database and configuration files before upgrading.
  4. 4. Follow the standard Mattermost upgrade procedure: stop the server, replace the binary/files, run any database migrations, and restart the server.
  5. 5. Verify the upgrade was successful by checking the version in the system console.
Caveat Standard Mattermost minor version upgrades typically have no breaking changes, but review release notes for any behavior changes

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

Fix this in Mattermost Server Scoped from the published advisory
  • Consultation6.0 h
  • Implementation16.0 h
  • Testing12.0 h
  • Review / QA6.0 h
40.0 hours of engineering $6,960
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $11,136.

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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-2025-12419 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