CVE-2026-8683: Mattermost Desktop

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

Mattermost Desktop App versions <=6.1 5.5.13.0 fail to account for attempting to open extremely long URLs in the Mattermost Desktop App which allows a malicious server owner to crash the application via including a script to call window.open on a very large URL. Mattermost Advisory ID: MMSA-2026-00652

Affected products

• Mattermost Mattermost Desktop: up to and including 5.13.0; from 6.1.0, up to and including 6.1.5

Published 2026-06-15. Last modified 2026-06-17.