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

Description (CNA)

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 (CNA)

Vendor / product	Versions
Mattermost / Mattermost	affected 11.7.0 through 11.7.0; affected 11.6.0 through 11.6.2; affected 11.5.0 through 11.5.5; affected 10.11.0 through 10.11.17; unaffected 11.8.0; unaffected 11.7.1; unaffected 11.6.3; unaffected 11.5.6; unaffected 10.11.18

CWE

CWE-862

References

https://mattermost.com/security-updates

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.