CVE-2026-16044: Mattermost Server

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

Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21 fail to prevent guest users from receiving Board Admin privileges during board archive import which allows a board member to escalate a guest user to Board Admin via importing a crafted .boardarchive file. Mattermost Advisory ID: MMSA-2026-00672

Affected products

• Mattermost Mattermost Server: from 10.11.0, before 10.11.22 (fixed in 10.11.22); from 11.7.0, before 11.7.7 (fixed in 11.7.7)

Published 2026-08-17. Last modified 2026-08-18.