dbcve.org
Mattermost ServerApplication · Mattermost

CVE-2025-13821

MEDIUM · 5.7 CVSS v3.1 Published 2026-02-16
Fix available
A fix is available. Upgrade to 10.11.10 / 11.1.3 or later.
See remediation →
61/100
Remediation priority · Elevated
Remotely reachable

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 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to sanitize sensitive data in WebSocket messages which allows authenticated users to exfiltrate password hashes and MFA secrets via profile nickname updates or email verification events. Mattermost Advisory ID: MMSA-2025-00560

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 sanitize sensitive data in WebSocket messages, allowing authenticated users to receive password hashes and MFA secrets through profile nickname updates or email verification events. The vulnerability stems from improper handling of sensitive credential data during WebSocket communication.

MitigationUpgrade to Mattermost versions 11.1.3, 10.11.10, or 11.2.2 or later to patch the insufficient sanitization of sensitive data in WebSocket messages.

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, < 10.11.10>= 11.1.0, < 11.1.3>= 11.2.0, < 11.2.2

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
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/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 Mattermost Server version
    Run `mattermost version` or check the version displayed in the System Console under About > Mattermost, or inspect the binary file version metadata
    Affected if The installed version falls within the ranges >= 10.11.0 and < 10.11.10, >= 11.1.0 and < 11.1.3, or >= 11.2.0 and < 11.2.2
  2. Confirm WebSocket endpoint is accessible
    Verify that the WebSocket endpoint at /api/v4/websocket is reachable by attempting a connection or checking the server configuration for EnableWebSocketEndpoint setting set to true
    Affected if WebSocket endpoint is enabled and the server version is in the affected ranges (WebSocket is enabled by default)
  3. Monitor WebSocket traffic for sensitive data exposure
    Use browser developer tools or a network proxy to inspect WebSocket messages sent to authenticated clients, specifically looking for payload fields containing password hashes or MFA secrets during profile nickname updates or email verification events
    Affected if WebSocket messages contain plaintext or hashed password data or MFA secret tokens in fields that should not be transmitted to clients

A user is affected if their Mattermost Server version is within the listed vulnerable ranges and they have WebSocket communication enabled, which allows authenticated users to potentially receive sensitive credential data through normal application events.

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 10.11.10 / 11.1.3 / 11.2.2 or later
Fixed in 10.11.1011.1.311.2.2
Interim mitigation

Upgrade to Mattermost versions 11.1.3, 10.11.10, or 11.2.2 or later to patch the insufficient sanitization of sensitive data in WebSocket messages.

Recommended fix High confidence

Upgrade to Mattermost Server 10.11.10 (for 10.11.x), 11.1.3 (for 11.1.x), or 11.2.2 (for 11.2.x) - recommended: 11.2.2 or latest stable

  1. 1. Back up your Mattermost database and configuration files before upgrading.
  2. 2. Determine your current Mattermost Server version (check System Console > About).
  3. 3. If running 10.11.x (10.11.0-10.11.9), upgrade to version 10.11.10 or later.
  4. 4. If running 11.1.x (11.1.0-11.1.2), upgrade to version 11.1.3 or later.
  5. 5. If running 11.2.x (11.2.0-11.2.1), upgrade to version 11.2.2 or later.
  6. 6. For the safest path, upgrade to the latest stable release (11.2.2 or later).
  7. 7. Follow Mattermost upgrade documentation for your deployment method (manual, Docker, Kubernetes, etc.).
  8. 8. After upgrade, verify the server is operational and test WebSocket functionality.
Caveat Minor version upgrades typically do not introduce breaking changes, but review release notes for deprecations and 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
  • Consultation2.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,100
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,960.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2025-13821 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2025-13821 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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