CVE-2026-26304: Mattermost Server

Medium severity, CVSS 4.3. EPSS: 0.3% chance of exploitation in the next 30 days.

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2 fail to verify run_create permission for empty playbookId, which allows team members to create unauthorized runs via the playbook run API. Mattermost Advisory ID: MMSA-2025-00542

Affected products

• Mattermost Mattermost Server: from 11.2.0, before 11.2.3 (fixed in 11.2.3); from 11.3.0, before 11.3.1 (fixed in 11.3.1)

Published 2026-03-16. Last modified 2026-06-17.