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Mattermost ServerApplication · Mattermost

CVE-2026-28741

HIGH · 8.1 CVSS v3.1 Published 2026-04-15
Fix available
A fix is available. Upgrade to 10.11.13 / 11.3.3 or later.
See remediation →
88/100
Remediation priority · High
Remotely reachable No privileges

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 10.11.x <= 10.11.12, 11.5.x <= 11.5.0, 11.4.x <= 11.4.2, 11.3.x <= 11.3.2 fail to validate CSRF tokens on an authentication endpoint which allows an attacker to update a user's authentication method via a CSRF attack by tricking a user into visiting a malicious page. Mattermost Advisory ID: MMSA-2026-00625

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 validate CSRF tokens on an authentication endpoint, allowing attackers to craft malicious pages that trick authenticated users into unknowingly changing their authentication method. This is a classic CSRF vulnerability where the server does not verify that requests originate from the legitimate application.

MitigationUpgrade to patched Mattermost versions beyond 10.11.12, 11.5.0, 11.4.2, or 11.3.2. As an interim measure, users should avoid visiting untrusted pages while authenticated.

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:>= 10.11.0, < 10.11.13>= 11.3.0, < 11.3.3>= 11.4.0, < 11.4.3>= 11.5.0, < 11.5.1

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
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

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. Identify installed Mattermost Server version
    Check the version via the Mattermost system console (go to System Console > About) or by making a GET request to the API endpoint /api/v4/system/stats/public, or inspect the version file in the Mattermost installation directory
    Affected if Installed version falls within >= 10.11.0, < 10.11.13; >= 11.3.0, < 11.3.3; >= 11.4.0, < 11.4.3; or >= 11.5.0, < 11.5.1
  2. Confirm CSRF protection on authentication endpoints
    Inspect HTTP responses from authentication-related endpoints (such as /api/v4/users/me/mfa or account settings endpoints that handle authentication method changes) to verify that the server returns and validates CSRF tokens in request headers
    Affected if The server does not require or validate CSRF tokens for authentication method change requests
  3. Verify if authentication method change feature is accessible
    Check the Mattermost config.json file for enabled authentication providers (such as LDAP, SAML, or OAuth) under PluginSettings, ServiceSettings, or LdapSettings, and determine if users have access to change their authentication method through account settings
    Affected if Users can access and modify authentication methods (e.g., enabling/disabling MFA, linking OAuth accounts) while the server runs a vulnerable version

You are affected if your Mattermost Server version is within the vulnerable ranges AND the authentication method change feature is accessible to users without proper CSRF token validation.

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 10.11.13 / 11.3.3 / 11.4.3 or later
Fixed in 10.11.1311.3.311.4.3
Interim mitigation

Upgrade to patched Mattermost versions beyond 10.11.12, 11.5.0, 11.4.2, or 11.3.2. As an interim measure, users should avoid visiting untrusted pages while authenticated.

Recommended fix High confidence

Upgrade to the appropriate fixed version: 10.11.13 (for 10.11.x), 11.3.3 (for 11.3.x), 11.4.3 (for 11.4.x), or 11.5.1 (for 11.5.x)

  1. 1. Identify the currently installed Mattermost Server version using the system console or mmctl command
  2. 2. Determine which version branch your installation falls into (10.11.x, 11.3.x, 11.4.x, or 11.5.x)
  3. 3. For 10.11.x branch: Upgrade to version 10.11.13 or later
  4. 4. For 11.3.x branch: Upgrade to version 11.3.3 or later
  5. 5. For 11.4.x branch: Upgrade to version 11.4.3 or later
  6. 6. For 11.5.x branch: Upgrade to version 11.5.1 or later
  7. 7. Review Mattermost upgrade documentation for your installation method (manual, Docker, Kubernetes, etc.)
  8. 8. Create a complete backup of the database and file storage before upgrading
Caveat Review Mattermost release notes for your target version as minor version upgrades may include feature changes; ensure plugin compatibility before upgrading

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

Fix this in Mattermost Server Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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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-2026-28741 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