CVE-2025-12559: Mattermost Server

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

Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to sanitize team email addresses to be visible only to Team Admins, which allows any authenticated user to view team email addresses via the GET /api/v4/channels/{channel_id}/common_teams endpoint

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); from 10.12.0, before 10.12.2 (fixed in 10.12.2); from 11.0.0, before 11.0.3 (fixed in 11.0.3)

Published 2025-11-27. Last modified 2026-06-17.