CVE-2026-5139
Published:June 22, 2026
Updated:August 04, 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
Affected Packages
github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.5.1 <v11.5.6+incompatibleFix Suggestion:
Update to version v11.5.6+incompatiblegithub.com/mattermost/mattermost (GO):
Affected version(s) >=v10.11.0+incompatible <v10.11.18+incompatibleFix Suggestion:
Update to version v10.11.18+incompatiblegithub.com/mattermost/mattermost (GO):
Affected version(s) >=v11.6.1-rc1 <v11.6.3+incompatibleFix Suggestion:
Update to version v11.6.3+incompatibleRelated Resources (3)
Do you need more information?
Contact UsCVSS v4
Base Score:
5.3
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
LOW
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
LOW
Vulnerable System Availability
LOW
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
5.4
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
LOW
Weakness Type (CWE)
Missing Authorization
EPSS
Base Score:
0.29