CVE-2026-3524: Mattermost Legal Hold

High severity, CVSS 8.8. EPSS: 0.4% chance of exploitation in the next 30 days.

Mattermost Plugin Legal Hold versions <=1.1.4 fail to halt request processing after a failed authorization check in ServeHTTP which allows an authenticated attacker to access, create, download, and delete legal hold data via crafted API requests to the plugin's endpoints. Mattermost Advisory ID: MMSA-2026-00621

Affected products

• Mattermost Legal Hold: before 1.1.5 (fixed in 1.1.5)

Published 2026-04-06. Last modified 2026-08-06.