CVE-2025-27715: Mattermost Server

Low severity, CVSS 2.7. EPSS: 0.2% chance of exploitation in the next 30 days.

Mattermost versions 9.11.x <= 9.11.8 fail to prompt for explicit approval before adding a team admin to a private channel, which team admins to joining private channels via crafted permalink links without explicit consent from them.

Affected products

• Mattermost Mattermost Server: from 9.11.0, before 9.11.9 (fixed in 9.11.9)

Published 2025-03-21. Last modified 2026-06-17.