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CVE-2026-5139

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

Published: Jun 22, 2026Updated: Jun 22, 2026 Sources: CVE List NVDCWE-862
NVD MITRE
5.4CVSSMEDIUM
EPSS Score
N/A
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

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

CVSS Vector Breakdown

AV:NAC:LPR:LUI:NS:UC:NI:LA:L
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:LPrivileges Required
Low
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:LIntegrity
Low
A:LAvailability
Low
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Weaknesses

CWE-862

Affected Products

MattermostMattermost
On-premWeb App
Communications / messaging-chat
mattermostcommercialUSCommunications

Attack Graph

Products CVE Techniques Tactics

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Exploitability

Official Patch Available

MITRE ATT&CK

2 techniques
Initial Access
View detailed technique mapping

References

https://mattermost.com/security-updates
mattermost.com

Timeline

Published
Jun 22, 2026
Last Updated
Jun 22, 2026

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