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Mattermost ServerApplication · Mattermost

CVE-2023-6547

MEDIUM · 5.4 CVSS v3.1 Published 2023-12-12
Fix available
A fix is available. Upgrade to after 9.2.1 or later.
See remediation →
60/100
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 validate team membership when a user attempts to access a playbook, allowing a user with permissions to a playbook but no permissions to the team the playbook is on to access and modify the playbook. This can happen if the user was once a member of the team, got permissions to the playbook and was then removed from the team. 

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 team membership when a user attempts to access a playbook. A user who previously had team membership, was granted playbook permissions, and was then removed from the team can still access and modify that playbook without proper team authorization.

MitigationImplement server-side validation to verify team membership before allowing access to playbooks, ensuring users must belong to the team to access any of its resources.

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:<= 8.1.5>= 9.2.0, <= 9.2.1

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/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
    Run the command `mattermost version` or access the System Console > About page to retrieve the exact version number installed.
    Affected if The version is <= 8.1.5 OR >= 9.2.0 AND <= 9.2.1
  2. Verify playbooks plugin is enabled
    Navigate to System Console > Plugins > Plugin Management and confirm the 'Playbooks' plugin is installed and enabled.
    Affected if The playbooks plugin is enabled (the vulnerability only applies when playbooks are active)
  3. Check for users removed from teams who still have playbook access
    Query the database or use the Mattermost API to list playbooks and their associated users, then cross-reference with current team membership using the Teams API or System Console > Users to identify users who are NOT currently members of the team but are listed as having playbook permissions or can still modify playbooks.
    Affected if Any user is found who can access or modify a playbook for a team they are no longer a member of

You are affected if your Mattermost Server version falls within <= 8.1.5 or >= 9.2.0 <= 9.2.1 AND the playbooks plugin is enabled AND a user who was removed from a team can still access that team's playbooks.

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 a release after 9.2.1
Interim mitigation

Implement server-side validation to verify team membership before allowing access to playbooks, ensuring users must belong to the team to access any of its resources.

Recommended fix High confidence

Upgrade to Mattermost Server 8.1.6+ (for 8.1.x line) or 9.2.2+ (for 9.2.x line). Latest stable releases in each supported branch are recommended.

  1. 1. Identify the currently installed Mattermost Server version by checking the system console or running 'mmctl version' if available.
  2. 2. For Mattermost Server 8.1.x (versions 8.1.5 and below): Plan an upgrade to version 8.1.6 or later in the 8.1.x stable release line.
  3. 3. For Mattermost Server 9.2.x (versions 9.2.0 through 9.2.1): Plan an upgrade to version 9.2.2 or later in the 9.2.x stable release line.
  4. 4. Before upgrading, backup the database and configuration files following Mattermost backup procedures.
  5. 5. Review the Mattermost upgrade guide for your deployment type (docker, helm, or manual) and perform the upgrade.
  6. 6. After upgrade, verify that the Mattermost server starts successfully and check the system console for any errors.
  7. 7. Test playbook access: Create a test scenario where a user is granted playbook permissions but removed from the team, and verify they can no longer access the playbook.
Caveat Review Mattermost release notes for the target version as there may be database migrations and feature changes between versions. Test upgrade in a staging environment first.

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
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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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-2023-6547 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