CVE-2026-4286: Mattermost Server

Medium severity, CVSS 4.3. EPSS: 0.2% chance of exploitation in the next 30 days.

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to check if {{team_id}} was being changed when updating playbooks, allowing users with only {{Manage Playbook Configurations}} permission to change a playbook's team, bypassing manage members restriction via PUT api. Mattermost Advisory ID: MMSA-2025-00552

Affected products

• Mattermost Mattermost Server: from 10.11.0, before 10.11.14 (fixed in 10.11.14); from 11.5.0, before 11.5.2 (fixed in 11.5.2)

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