CVE-2026-5139

MEDIUM

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

Title source: cna
STIX 2.1

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

References (1)

Core 1
Core References
Vendor Advisory vendor-advisory
MMSA-2026-00644
https://mattermost.com/security-updates

Scores

CVSS v3 5.4
EPSS 0.0017
EPSS Percentile 6.6%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L

CISA SSVC

Vulnrichment
Exploitation none
Automatable no
Technical Impact partial

Details

CWE
CWE-862
Status published
Products (10)
Mattermost/Mattermost 10.11.0 - 10.11.17
Mattermost/Mattermost 10.11.18
Mattermost/Mattermost 11.5.0 - 11.5.5
Mattermost/Mattermost 11.5.6
Mattermost/Mattermost 11.6.0 - 11.6.2
Mattermost/Mattermost 11.6.3
Mattermost/Mattermost 11.7.0
Mattermost/Mattermost 11.7.1
Mattermost/Mattermost 11.8.0
mattermost/mattermost_server 10.11.0 - 10.11.18
Published Jun 22, 2026
Tracked Since Jun 22, 2026