CVE-2026-3117: Mattermost Server

Medium severity, CVSS 6.5. EPSS: 0.4% chance of exploitation in the next 30 days.

Mattermost Plugins versions <=11.5 11.1.5 10.13.11 11.3.4.0 fail to properly check for permissions when processing commands in the Gitlab plugin which allows normal users to uninstall instances or setup webhook connections via the {{gitlab instance {option}}} or the {{/gitlab webhook {option}}} commands. Mattermost Advisory ID: MMSA-2026-00600

Affected products

• Mattermost Mattermost Server: from 10.13.0, up to and including 10.13.11; from 11.1.0, up to and including 11.1.5; from 11.3.0, up to and including 11.3.4

Published 2026-05-18. Last modified 2026-06-17.