CVE-2025-13767: Mattermost Server

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

Mattermost versions 11.1.x <= 11.1.0, 11.0.x <= 11.0.5, 10.12.x <= 10.12.3, 10.11.x <= 10.11.7 fails to validate user channel membership when attaching Mattermost posts as comments to Jira issues, which allows an authenticated attacker with access to the Jira plugin to read post content and attachments from channels they do not have access to.

Affected products

• Mattermost Mattermost Server: from 10.11.0, before 10.11.8 (fixed in 10.11.8); from 10.12.0, before 10.12.4 (fixed in 10.12.4); from 11.0.0, before 11.0.6 (fixed in 11.0.6); from 11.1.0, before 11.1.1 (fixed in 11.1.1)

Published 2025-12-24. Last modified 2026-06-17.