CVE-2026-9859

published 2026-08-17

CVE-2026-9859: 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…

Priority P3 42 medium 6.5 CVSS 3.1

AV N AC L PR L UI N S U C H I N A N

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

Affected

6 ranges

Vendor	Product	Version range	Fixed in
mattermost	mattermost	10.11.0 – 10.11.21	—
mattermost	mattermost	11.7.0 – 11.7.6	—
mattermost	mattermost	11.8.0 – 11.8.3	—
mattermost	mattermost_server	>= 10.11.0 < 10.11.22	10.11.22
mattermost	mattermost_server	>= 11.7.0 < 11.7.7	11.7.7
mattermost	mattermost_server	>= 11.8.0 < 11.8.4	11.8.4

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CWE-863