CVE-2026-9602: Mattermost Desktop

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

Mattermost Desktop App versions <=6.2 6.0.2 5.6.13.0 fail to validate payloads sent from the Mattermost Web App to the Desktop App which allows a malicious server owner to crash the Mattermost Desktop App via changing the payload of a method to a malformed one. Mattermost Advisory ID: MMSA-2026-00678

Affected products

• Mattermost Mattermost Desktop: from 5.6.13, before 5.13.7 (fixed in 5.13.7); from 6.0.2, before 6.2.1 (fixed in 6.2.1); after 6.2.1, before 6.3 (fixed in 6.3)

Published 2026-07-17. Last modified 2026-07-30.