CVE-2026-16047
Medium
Description
Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing, or bulk-creating boards with an arbitrary channelId. Mattermost Advisory ID: MMSA-2026-00674
SeverityMedium
CVSS4.3
Exploit probability—
Product
Mattermost Server
PublishedAug 17, 2026
First seenAug 17, 2026
Weakness typeCWE-862Missing authorization
How to fix
Update
- mattermost mattermost_server10.11.22, 11.7.7, 11.8.4 or later
Vendor advisories
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mattermost mattermost_server | 10.11.0 ≤ v < 10.11.22, 11.7.0 ≤ v < 11.7.7, 11.8.0 ≤ v < 11.8.4 | 10.11.22, 11.7.7, 11.8.4 |
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