CVE-2025-35965: Mattermost Server

High severity, CVSS 7.5. EPSS: 0.4% chance of exploitation in the next 30 days.

Mattermost versions 10.4.x <= 10.4.2, 10.5.x <= 10.5.0, 9.11.x <= 9.11.10 fail to validate the uniqueness and quantity of task actions within the UpdateRunTaskActions GraphQL operation, which allows an attacker to create task items containing an excessive number of actions triggered by specific posts, overloading the server and leading to a denial-of-service (DoS) condition.

Affected products

• Mattermost Mattermost Server: from 9.11.0, before 9.11.11 (fixed in 9.11.11); from 10.4.0, before 10.4.3 (fixed in 10.4.3); version 10.5.0 only

Published 2025-04-24. Last modified 2026-06-17.