dbcve.org
Mattermost ServerApplication · Mattermost

CVE-2025-9081

MEDIUM · 6.5 CVSS v3.1 Published 2025-09-19
Fix available
A fix is available. Upgrade to 9.11.17 / 10.5.9 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 versions 10.5.x <= 10.5.8, 9.11.x <= 9.11.17 fail to properly validate access controls which allows any authenticated user to download sensitive files via board file download endpoint using UUID enumeration

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 access controls on the board file download endpoint, allowing any authenticated user to download sensitive files via UUID enumeration. This is an Insecure Direct Object Reference (IDOR) vulnerability where the application does not verify that the requesting user has permission to access the specific file before serving it.

MitigationUpgrade Mattermost to versions 10.5.9+ or 9.11.18+ which contain proper access control validation for the board file download endpoint.

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:>= 9.11.0, < 9.11.17>= 10.5.0, < 10.5.9

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
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/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 installation
    Check for Mattermost Server by looking for the mattermost binary at /opt/mattermost/bin/mattermost, or check running services via 'systemctl list-units | grep mattermost' or 'docker ps | grep mattermost'. Also check for the mattermost config directory at /opt/mattermost/config.
    Affected if Mattermost Server is not found on the system
  2. Determine installed Mattermost version
    Run 'mattermost version' if the binary is accessible, or check the version file typically located at /opt/mattermost/version.txt. If using Docker, check with 'docker exec <container> mattermost version'. The version is also visible in the system console under About > Mattermost.
    Affected if Unable to determine the installed version from the system
  3. Compare version against affected ranges
    Review the detected version against: 9.11.0 through 9.11.16 (inclusive), or 10.5.0 through 10.5.8 (inclusive). Versions 9.11.17+ and 10.5.9+ are patched.
    Affected if The installed version is 9.11.0-9.11.16 or 10.5.0-10.5.8, placing it within the affected range
  4. Verify if Boards plugin is enabled
    In Mattermost, go to System Console > Plugins > Plugin Management, or check the plugins section in the config.json file at /opt/mattermost/config/config.json for the 'boards' plugin entry. The vulnerability affects the boards file download endpoint.
    Affected if Boards plugin is enabled and the version falls within affected ranges

A user is affected if Mattermost Server version is 9.11.0-9.11.16 or 10.5.0-10.5.8 AND the Boards plugin is enabled.

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 9.11.17 / 10.5.9 or later
Fixed in 9.11.1710.5.9
Interim mitigation

Upgrade Mattermost to versions 10.5.9+ or 9.11.18+ which contain proper access control validation for the board file download endpoint.

Recommended fix High confidence

Upgrade to Mattermost Server 9.11.17 (for 9.11.x branch) or 10.5.9 (for 10.5.x branch)

  1. Identify the currently running Mattermost Server version using the system console or /about command
  2. Backup the Mattermost database and configuration files before upgrading
  3. For Mattermost 9.11.x deployments: Upgrade to version 9.11.17 or later
  4. For Mattermost 10.5.x deployments: Upgrade to version 10.5.9 or later
  5. After upgrade, verify the board file download endpoint no longer allows unauthorized access to files via UUID enumeration
  6. Test that legitimate file access through the boards feature still works correctly
Caveat Review Mattermost release notes for any breaking changes between your current version and the target version before upgrading

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

Fix this in Mattermost Server Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing8.0 h
  • Review / QA4.0 h
24.0 hours of engineering $4,160
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,656.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2025-9081 — 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-2025-9081 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