CVE-2026-5139GitLab Plugin Allows Non-Admin Users to Modify Default Instance Configuration
- 5.4MediumCVSS base score
- 0.29%Exploitation in 30 daysEPSS · top 78% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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
Timeline
ID reserved
By Mattermost
- 3 months later
· 3 months later
Published
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| MattermostCNA (assigner) | 3.1 | Medium5.4 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L |
| NVDNVD · Analyzed | 3.1 | Medium5.4 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L |
- EPSS (exploitation in 30 days)
- 0.29% · top 78% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.4.
Affected products
- affected 11.7.0 – ≤ 11.7.0
- affected 11.6.0 – ≤ 11.6.2
- affected 11.5.0 – ≤ 11.5.5
- affected 10.11.0 – ≤ 10.11.17
- unaffected 11.8.0
- unaffected 11.7.1
- unaffected 11.6.3
- unaffected 11.5.6
- unaffected 10.11.18
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- Gogithub.com/mattermost/mattermost-serverGHSA-2g8v-grq3-hq2g (opens in a new tab)
What to do
Solution: Update Mattermost to versions 11.8.0, 11.7.1, 11.6.3, 11.5.6, 10.11.18 or higher.
References
References1
- MMSA-2026-00644 (opens in a new tab)vendor-advisory
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-38246 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-2g8v-grq3-hq2g (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-5139)Record last updated .