CVE-2026-5139 | Mattermost versions 11.7.x <= 11.7.0, 11.6.x <= 11.6.2, 11.5… | CVSS 5.4 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

Metadata

CVE ID: CVE-2026-5139
State: PUBLISHED
Assigner: Mattermost
Reserved: 2026-03-30 11:29 UTC
Published: 2026-06-22 13:34 UTC
Last updated: 2026-06-22 15:39 UTC
Primary CWE: CWE-862
CWE-862: Missing Authorization
Vendor / Product: Mattermost / Mattermost
Sources: cve.org · NVD

Severity & Metrics

5.4 MEDIUM CVSS 3.1

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

SSVC — CISA Coordinator

Exploitation: none
Automatable: no
Tech. Impact: partial

Affected products (1)

Vendor	Product	Platform	Versions
Mattermost	Mattermost	—	11.7.0 ≤ 11.7.0, 11.6.0 ≤ 11.6.2, 11.5.0 ≤ 11.5.5, 10.11.0 ≤ 10.11.17 …

Weakness (CWE)

CWE	Source	Description
CWE-862	cna	CWE-862: Missing Authorization

CVSS scores (1)

Score	Severity	Version	Source	Vector
5.4	MEDIUM	3.1	cna	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L

References (1)

MMSA-2026-00644 https://mattermost.com/security-updates