CVE-2025-9072: Mattermost Server

Medium severity, CVSS 5.4. EPSS: 0.2% chance of exploitation in the next 30 days.

Mattermost versions 10.10.x <= 10.10.1, 10.5.x <= 10.5.9, 10.9.x <= 10.9.4 fail to validate the redirect_to parameter, allowing an attacker to craft a malicious link that, once a user authenticates with their SAML provider, could post the user’s cookies to an attacker-controlled URL.

Affected products

• Mattermost Mattermost Server: from 10.5.0, before 10.5.10 (fixed in 10.5.10); from 10.9.0, before 10.9.5 (fixed in 10.9.5); from 10.10.0, before 10.10.2 (fixed in 10.10.2)

Published 2025-09-15. Last modified 2026-06-17.