CVE-2026-5139
GitLab Plugin Allows Non-Admin Users to Modify Default Instance Configuration
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
INFO
Published Date :
June 22, 2026, 1:34 p.m.
Last Modified :
June 22, 2026, 1:34 p.m.
Remotely Exploit :
Yes !
Source :
Mattermost
Affected Products
The following products are affected by CVE-2026-5139
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | 9302f53e-dde5-4bf3-b2f2-a83f91ac0eee | ||||
| CVSS 3.1 | MEDIUM | MITRE-CVE |
Solution
- Update Mattermost to a patched version.
- Verify authorization controls for /gitlab connect.
- Restrict access to the /gitlab connect command.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-5139 vulnerability anywhere in the article.