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
Metrics
CVSS 3.1 4.3/10
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:NWeakness enumeration
Affected software
| Vendor | Product | Versions |
|---|---|---|
| Mattermost | Mattermost | >= 11.7.0, <= 11.7.6; >= 10.11.0, <= 10.11.21; >= 11.8.0, <= 11.8.3 |
References
- https://mattermost.com/security-updatesVendor Advisory
Timeline
- Published
- Aug 17, 2026
- Last modified
- Aug 18, 2026
- NVD status
- Analyzed