CVE-2026-5139 json
GitLab Plugin Allows Non-Admin Users to Modify Default Instance Configuration
published 2026-06-22 4 mo ago modified 2026-09-28 41 d ago also GHSA-2g8v-grq3-hq2g , GO-2026-6480 , EUVD-2026-38246
- cvss
- 5.4
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.3%
- EPSS 0.3% chance of exploitation in 30 days, percentile 21%
- public exploits
- 0
- none known
Summary
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
Patch / fix
- go github.com/mattermost/mattermost-server 10.11.18, 10.11.18+incompatible, 11.5.6, 11.5.6+incompatible, 11.6.3, 11.6.3+incompatible, 11.7.1, 11.7.1+incompatible
- Mattermost Mattermost 10.11.18, 11.5.6, 11.6.3, 11.7.1, 11.8.0
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 4 mo ago
Exploit prediction
0.29% chance of exploitation in the next 30 days, higher than 21% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 5.4 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L |
| GitHub | 3.1 | 5.4 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| go | github.com/mattermost/mattermost-server | >=11.7.0, <11.7.1 >=11.6.0, <11.6.3 >=11.5.0, <11.5.6 >=10.11.0, <10.11.18 >=10.11.0+incompatible, <10.11.18+incompatible >=11.5.0+incompatible, <11.5.6+incompatible >=11.6.0+incompatible, <11.6.3+incompatible >=11.7.0+incompatible, <11.7.1+incompatible |
11.7.1 11.6.3 11.5.6 10.11.18 10.11.18+incompatible 11.5.6+incompatible 11.6.3+incompatible 11.7.1+incompatible |
Affected products
- Mattermost Mattermost
Classification
- Weakness
-
- CWE-862 Missing Authorization
References
-
mattermost.com
/security-updates
vendor-advisory, web
-
nvd.nist.gov
/vuln/detail/CVE-2026-5139
advisory
-
github.com
/mattermost/mattermost
package
-
github.com
/advisories/GHSA-2g8v-grq3-hq2g
advisory
Sources
- CVE List CVE-2026-5139
- GitHub Advisory GHSA-2g8v-grq3-hq2g
- NVD CVE-2026-5139
- OSV GO-2026-6480
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.