CVE-2026-10085: Mattermost Server

Medium severity, CVSS 5.4. EPSS: 0.3% chance of exploitation in the next 30 days.

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to restrict the group_constrained channel flag to public and private channels that support group synchronization, which allows an ordinary group or direct message member to remove all participants from the conversation via the channel patch API.. Mattermost Advisory ID: MMSA-2026-00688

Affected products

• Mattermost Mattermost Server: from 10.11.0, before 10.11.20 (fixed in 10.11.20); from 11.6.0, before 11.6.5 (fixed in 11.6.5); from 11.7.0, before 11.7.3 (fixed in 11.7.3)

Published 2026-07-13. Last modified 2026-07-14.