CVE-2025-13870: Mattermost Server

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

Mattermost versions 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to validate the user permission when accessing the files and subscribing to the block in Boards, which allows an authenticated user to access other board files and was able to subscribe to the block from other boards that the user does not have access to

Affected products

• Mattermost Mattermost Server: from 10.5.0, before 10.5.13 (fixed in 10.5.13); from 10.11.0, before 10.11.5 (fixed in 10.11.5)

Published 2025-12-02. Last modified 2026-06-17.