# CVE-2026-5139: GitLab Plugin Allows Non-Admin Users to Modify Default Instance Configuration

> CVE-2026-5139: GitLab Plugin Allows Non-Admin Users to Modify Default Instance Configuration. CVSS 5.4 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-5139
Last updated: 2026-06-23T20:50:51Z

- Published: 2026-06-22 13:34 UTC · Updated: 2026-06-23 20:50 UTC · Assigner: Mattermost
- CVSS: 5.4 (CVSS 3.1) · Severity: Medium · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
- EPSS: 0.29%, 21th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-862

## 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

## Affected vendors and products

- Mattermost: Mattermost

## Tracked companies

- [Mattermost](https://rewindex.com/company/mattermost.md)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-5139)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-5139)
- [https://mattermost.com/security-updates](https://mattermost.com/security-updates)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2026-5139 · Markdown: https://rewindex.com/cve/CVE-2026-5139.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-5139 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:15:31.218Z