CVE-2026-9859
Mattermost Boards plugin didn’t enforce role-based authorization on board channel link allowing board editors to expose boards to arbitrary channels
CVSS Score
6.5
EPSS Score
0.0%
EPSS Percentile
0th
Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to enforce PermissionManageBoardRoles on the channelId field of the batch endpoint, which allows an authenticated board editor to relink any board they can edit to an arbitrary channel via a crafted PATCH request. Mattermost Advisory ID: MMSA-2026-00686
| CWE | CWE-863 |
| Vendor | mattermost |
| Product | mattermost |
| Published | Aug 17, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None
Affected Versions
Mattermost / Mattermost
11.7.0 ≤ 11.7.6 10.11.0 ≤ 10.11.21 11.8.0 ≤ 11.8.3
Credits
kauasilvab14fb3