CVE-2025-55073: Mattermost Server

Medium severity, CVSS 5.3. EPSS: 0.2% chance of exploitation in the next 30 days.

Mattermost versions 10.11.x <= 10.11.3, 10.5.x <= 10.5.11, 10.12.x <= 10.12.0 fail to validate the relationship between the post being updated and the MSTeams plugin OAuth flow which allows an attacker to edit arbitrary posts via a crafted MSTeams plugin OAuth redirect URL.

Affected products

• Mattermost Mattermost Server: from 10.5.0, before 10.5.12 (fixed in 10.5.12); from 10.11.0, before 10.11.4 (fixed in 10.11.4); from 10.12.0, before 10.12.1 (fixed in 10.12.1)

Published 2025-11-14. Last modified 2026-06-17.