CVE-2026-5139
Medium
Description
Mattermost versions 11.7.x <= 11.7.0, 11.6.x <= 11.6.2, 11.5.x <= 11.5.5, 10.11.x <= 10.11.17 fail to enforce administrator authorization on the {{setDefaultInstance}} call within the {{/gitlab connect}} command handler, which allows any authenticated user to overwrite the global default GitLab instance configuration via the {{/gitlab connect <instance-name>}} slash command.. Mattermost Advisory ID: MMSA-2026-00644
SeverityMedium
CVSS5.4
Exploit probability—
Product
Mattermost Server
PublishedJun 22, 2026
First seenJun 22, 2026
Weakness typeCWE-862Missing authorization
How to fix
Update
- mattermost mattermost_server10.11.18, 11.5.6, 11.6.3, 11.7.1 or later
- github.com/mattermost/mattermost-server11.7.1, 11.6.3, 11.5.6, 10.11.18, 10.11.18+incompatible, 11.5.6+incompatible, 11.6.3+incompatible, 11.7.1+incompatible or later
Vendor advisories
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mattermost mattermost_server | 10.11.0 ≤ v < 10.11.18, 11.5.0 ≤ v < 11.5.6, 11.6.0 ≤ v < 11.6.3, 11.7.0 ≤ v < 11.7.1 | 10.11.18, 11.5.6, 11.6.3, 11.7.1 |
| github.com/mattermost/mattermost-serverGo | 11.7.0 ≤ v < 11.7.1, 11.6.0 ≤ v < 11.6.3, 11.5.0 ≤ v < 11.5.6, 10.11.0 ≤ v < 10.11.18, 10.11.0+incompatible ≤ v < 10.11.18+incompatible, 11.5.0+incompatible ≤ v < 11.5.6+incompatible, 11.6.0+incompatible ≤ v < 11.6.3+incompatible, 11.7.0+incompatible ≤ v < 11.7.1+incompatible | 11.7.1, 11.6.3, 11.5.6, 10.11.18, 10.11.18+incompatible, 11.5.6+incompatible, 11.6.3+incompatible, 11.7.1+incompatible |
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