CVE-2026-96260: Mattermost Server

Medium severity, CVSS 6.5. EPSS: 0.4% chance of exploitation in the next 30 days.

Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to enforce a request body size limit during CSRF validation of plugin requests which allows an authenticated user to exhaust server memory and cause a denial of service via a large request body sent to a plugin endpoint.. Mattermost Advisory ID: MMSA-2026-00775

Affected products

• Mattermost Mattermost Server: from 11.7.0, before 11.7.11 (fixed in 11.7.11); from 11.8.0, before 11.8.6 (fixed in 11.8.6); from 11.9.0, before 11.9.2 (fixed in 11.9.2); from 11.10.0, before 11.10.2 (fixed in 11.10.2)

Published 2026-09-22. Last modified 2026-10-07.