ShellCodeX vulnerability brief
HIGH
Received
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
Published 17 Aug 2026, 22:17 UTC
Last modified 17 Aug 2026, 22:17 UTC
01
Attack profile
The conditions required to exploit this vulnerability and its potential impact.
Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
High
Availability
High
02
Affected products
Product applicability statements supplied with the NVD record.
NVD has not published structured affected-product data for this record.
03
Weakness classification
CWE categories help security teams group the underlying software weakness.
04
Source references
External advisories, patches and technical reports attached to this CVE record.