CVE-2025-27936: Mattermost Server

Medium severity, CVSS 5.9. EPSS: 0.3% chance of exploitation in the next 30 days.

Mattermost Plugin MSTeams versions <2.1.0 and Mattermost Server versions 10.5.x <=10.5.1 with the MS Teams plugin enabled fail to perform constant time comparison on a MSTeams plugin webhook secret which allows an attacker to retrieve the webhook secret of the MSTeams plugin via a timing attack during webhook secret comparison.

Affected products

• Mattermost Mattermost Server: before 10.5.2 (fixed in 10.5.2)
• Mattermost Ms Teams: before 2.1.0 (fixed in 2.1.0)

Published 2025-04-16. Last modified 2026-06-17.