CVE-2026-5139 PUBLISHED

GitLab Plugin Allows Non-Admin Users to Modify Default Instance Configuration

Assigner: Mattermost
Reserved: 30.03.2026 Published: 22.06.2026 Updated: 22.06.2026

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

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
CVSS Score: 5.4

Attack Vector	Network	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	None
Privileges Required	Low	Integrity Impact	Low
User Interaction	None	Availability Impact	Low

CVSS 3.1

Product Status

Vendor	Mattermost
Product	Mattermost
Versions	Default: unaffected affected from 11.7.0 to 11.7.0 (incl.) affected from 11.6.0 to 11.6.2 (incl.) affected from 11.5.0 to 11.5.5 (incl.) affected from 10.11.0 to 10.11.17 (incl.) Version 11.8.0 is unaffected Version 11.7.1 is unaffected Version 11.6.3 is unaffected Version 11.5.6 is unaffected Version 10.11.18 is unaffected

Solutions

Update Mattermost to versions 11.8.0, 11.7.1, 11.6.3, 11.5.6, 10.11.18 or higher.

Credits

hunterxluxhug finder

References

MMSA-2026-00644

Problem Types

CWE-862: Missing Authorization CWE