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Mattermost ServerApplication · Mattermost

CVE-2026-3117

MEDIUM · 6.5 CVSS v3.1 Published 2026-05-18
Fix available
A fix is available. Upgrade to after 11.3.4 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 Plugins versions <=11.5 11.1.5 10.13.11 11.3.4.0 fail to properly check for permissions when processing commands in the Gitlab plugin which allows normal users to uninstall instances or setup webhook connections via the {{gitlab instance {option}}} or the {{/gitlab webhook {option}}} commands. Mattermost Advisory ID: MMSA-2026-00600

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 · moderate confidence

The Mattermost Gitlab plugin fails to properly validate user permissions when processing the `gitlab instance` and `gitlab webhook` commands, allowing authenticated normal (non-privileged) users to perform administrative actions such as uninstalling Gitlab instances and configuring webhook connections that should require elevated privileges.

MitigationUpgrade the Mattermost Gitlab plugin to a version beyond the affected releases (11.5, 11.1.5, 10.13.11, 11.3.4.0). If immediate patching is not feasible, consider disabling the Gitlab plugin or restricting user access to plugin commands until the update can be applied.

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:>= 10.13.0, <= 10.13.11>= 11.1.0, <= 11.1.5>= 11.3.0, <= 11.3.4

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
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/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. Identify Mattermost Server version
    Access the Mattermost System Console and navigate to About > Edition and License, or use the Mattermost CLI: `mattermost version`. Compare the installed version against the affected ranges: 10.13.0-10.13.11, 11.1.0-11.1.5, or 11.3.0-11.3.4.
    Affected if The installed version falls within any of the listed affected version ranges.
  2. Confirm Gitlab plugin is installed
    Navigate to Mattermost System Console > Plugin Management, or use the CLI: `mattermost plugin list`. Look for the Gitlab plugin in the list of installed plugins.
    Affected if The Gitlab plugin appears in the installed plugins list.
  3. Check Gitlab plugin is enabled
    In Plugin Management, verify the Gitlab plugin status shows as Enabled. If using CLI: `mattermost plugin get <plugin-id>` to check enabled state.
    Affected if The Gitlab plugin is installed and enabled.
  4. Identify user role assignments
    Navigate to System Console > Users to review user roles. Normal (non-privileged) users with standard access to the system can exploit this vulnerability if they have access to run plugin commands.
    Affected if There are authenticated non-admin users with access to the Mattermost system who could invoke the gitlab instance or gitlab webhook commands.
  5. Verify plugin command access
    Test whether non-privileged users can access the /gitlab instance and /gitlab webhook slash commands. This can be checked by reviewing System Console > Integration Management > Bot Accounts or checking if slash commands are registered for all users.
    Affected if Non-admin users have the ability to execute plugin commands in channels they access.

You are affected if your Mattermost Server runs a version between 10.13.0-10.13.11, 11.1.0-11.1.5, or 11.3.0-11.3.4 AND the Gitlab plugin is enabled, allowing any authenticated user to potentially perform administrative actions.

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 11.3.4
Interim mitigation

Upgrade the Mattermost Gitlab plugin to a version beyond the affected releases (11.5, 11.1.5, 10.13.11, 11.3.4.0). If immediate patching is not feasible, consider disabling the Gitlab plugin or restricting user access to plugin commands until the update can be applied.

Recommended fix Moderate confidence

Mattermost Server 10.13.12+, 11.1.6+, 11.3.5+, or 11.5.1+ (whichever matches your major version branch)

  1. 1. Identify your current Mattermost Server version by checking the system console or running `mattermost version`
  2. 2. If running version 10.13.x (10.13.0 through 10.13.11), upgrade to version 10.13.12 or later
  3. 3. If running version 11.1.x (11.1.0 through 11.1.5), upgrade to version 11.1.6 or later
  4. 4. If running version 11.3.x (11.3.0 through 11.3.4), upgrade to version 11.3.5 or later
  5. 5. If running version 11.5.x, upgrade to version 11.5.1 or later (based on the advisory mentioning 11.5 as affected)
  6. 6. Review GitLab plugin permissions after upgrade to ensure only authorized admins can use gitlab instance and gitlab webhook commands
  7. 7. Test the plugin functionality with non-admin users to confirm the authorization fix is working
Caveat Minor upgrade within same major version should have minimal breaking changes; always review release notes for any migration notes

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
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,920
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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-2026-3117 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