CVE-2026-6739
Medium
Description
Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to require system-level permission when patching protected default system roles, which allows authenticated users with delegated user-management permissions to escalate privileges by altering built-in role permissions via the role patch API.. Mattermost Advisory ID: MMSA-2026-00656
SeverityMedium
CVSS6.7
Exploit probability—
Product
Mattermost Server
PublishedJun 12, 2026
First seenJun 12, 2026
Weakness typeCWE-863Incorrect authorization
How to fix
Update
- mattermost mattermost_server10.11.17, 11.5.5, 11.6.2 or later
- github.com/mattermost/mattermost-server11.6.1, 11.5.5, 10.11.17, 10.11.17+incompatible, 11.5.5+incompatible, 11.6.1+incompatible or later
- github.com/mattermost/mattermost/server/v88.0.0-20260501142004-99b73d4c4acf or later
Vendor advisories
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mattermost mattermost_server | 10.11.0 ≤ v < 10.11.17, 11.5.0 ≤ v < 11.5.5, 11.6.0 ≤ v < 11.6.2 | 10.11.17, 11.5.5, 11.6.2 |
| github.com/mattermost/mattermost-serverGo | 11.6.0 ≤ v < 11.6.1, 11.5.0 ≤ v < 11.5.5, 10.11.0 ≤ v < 10.11.17, 10.11.0+incompatible ≤ v < 10.11.17+incompatible, 11.5.0+incompatible ≤ v < 11.5.5+incompatible, 11.6.0+incompatible ≤ v < 11.6.1+incompatible | 11.6.1, 11.5.5, 10.11.17, 10.11.17+incompatible, 11.5.5+incompatible, 11.6.1+incompatible |
| github.com/mattermost/mattermost/server/v8Go | 8.0.0-20250731163400-5b955468ea1e ≤ v < 8.0.0-20260501142004-99b73d4c4acf | 8.0.0-20260501142004-99b73d4c4acf |
| github.com/mattermost/mattermost-server/v5Go | No range specified | — |
| github.com/mattermost/mattermost-server/v6Go | No range specified | — |
Check your version
Choose the product and enter the version you run to see whether it falls in the affected range.
In the Intelligence 360 plan
Attack Surface Management
See the assets tied to your domains, the technologies they run and known vulnerabilities in one list.