CVE-2026-9824: Mattermost Server

Medium severity, CVSS 4.3. 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 check the manage_shared_channels permission in the /share-channel autocomplete handler, which allows an authenticated user without that permission to enumerate configured remote cluster connection metadata via slash command autocomplete.. Mattermost Advisory ID: MMSA-2026-00676

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 2026-07-13.