CVE-2026-9816
High · CVSS 8.3Published 2026-08-17
CVSS
8.3
High
EPSS
—
exploit probability
Active Exploit
No
not yet listed
What is CVE-2026-9816?
Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to validate BoardMember.Scheme* fields server-side on insert and archive-import paths which allows a board editor or non-guest team member to grant board admin to arbitrary users via POST /api/v2/boards/{boardID}/members and POST /api/v2/teams/{teamID}/archive/import.. Mattermost Advisory ID: MMSA-2026-00685
CVSS Score Explained
CVSS 8.3 is High severity. Exploitation is likely straightforward and the impact is significant — data loss, privilege escalation, or remote code execution are common outcomes. Patch as soon as possible.
EPSS Exploitation Probability
No EPSS score yet — model needs more data on this CVE.
References & Patches
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