CVE-2026-5139 Details
Description
Mattermost versions 11.7.x <= 11.7.0, 11.6.x <= 11.6.2, 11.5.x <= 11.5.5, 10.11.x <= 10.11.17 fail to enforce administrator authorization on the {{setDefaultInstance}} call within the {{/gitlab connect}} command handler, which allows any authenticated user to overwrite the global default GitLab instance configuration via the {{/gitlab connect <instance-name>}} slash command.. Mattermost Advisory ID: MMSA-2026-00644
A vulnerability exists in Mattermost versions 11.7.x through 11.7.0, 11.6.x through 11.6.2, 11.5.x through 11.5.5, and 10.11.x through 10.11.17. The issue arises because these versions do not properly enforce administrator authorization on the 'setDefaultInstance' call within the '/gitlab connect' command handler. This flaw enables any authenticated user to overwrite the global default GitLab instance configuration using the '/gitlab connect <instance-name>' slash command.
Users can upgrade to Mattermost versions 11.8.0 or 11.7.0 to address this vulnerability.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jun 22, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://mattermost.com/security-updates | [email protected] | Vendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-862 | Missing Authorization | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| mattermost mattermost server | >= 10.11.0, < 10.11.18 >= 11.5.0, < 11.5.6 >= 11.6.0, < 11.6.3 >= 11.7.0, < 11.7.1 |
CPE
Remediation
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Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 23, 2026 | Initial Analysis | [email protected] |
| Jun 22, 2026 | CVE Modified | CISA-ADP |
| Jun 22, 2026 | New CVE Received | [email protected] |