CVE-2026-5139

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

State: Published
Severity: 5.4 Medium
Published: Jun 22, 2026
Updated: Jun 22, 2026
Reserved: Mar 30, 2026

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

Scores

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

Weaknesses

CWE-862 Missing Authorization

Affected Products

Product	Versions
MattermostMattermost	11.7.0 through 11.7.0Affected 11.6.0 through 11.6.2Affected 11.5.0 through 11.5.5Affected 10.11.0 through 10.11.17Affected 11.8.0Not affected 11.7.1Not affected 11.6.3Not affected 11.5.6Not affected 10.11.18Not affected

References

MMSA-2026-00644vendor-advisory

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