CVE-2025-8023: Mattermost Server

Medium severity, CVSS 4.9. EPSS: 0.4% chance of exploitation in the next 30 days.

Mattermost versions 10.8.x <= 10.8.3, 10.5.x <= 10.5.8, 9.11.x <= 9.11.17, 10.9.x <= 10.9.2 fails to sanitize path traversal sequences in template file destination paths, which allows a system admin to perform path traversal attacks via malicious path components, potentially enabling malicious file placement outside intended directories.

Affected products

• Mattermost Mattermost Server: from 9.11.0, before 9.11.18 (fixed in 9.11.18); from 10.5.0, before 10.5.9 (fixed in 10.5.9); from 10.8.0, before 10.8.4 (fixed in 10.8.4); from 10.9.0, before 10.9.3 (fixed in 10.9.3)

Published 2025-08-21. Last modified 2026-06-17.