CVE-2026-15754
Published:August 17, 2026
Updated:September 01, 2026
Mattermost versions 11.7.x <= 11.7.6, 11.8.x <= 11.8.3 The access control policy unassign endpoint fails to re-validate that each target channel still belongs to the requesting admin's team, which allows an authenticated team administrator to remove ABAC (attribute-based access control) policy assignments from channels outside their team via the policy unassign API after a channel has been moved to another team.. Mattermost Advisory ID: MMSA-2026-00718
Affected Packages
https://github.com/mattermost/mattermost.git (GITHUB):
Affected version(s) >=v11.7.0 <v11.7.7Fix Suggestion:
Update to version v11.7.7https://github.com/mattermost/mattermost.git (GITHUB):
Affected version(s) >=v11.8.0 <v11.8.4Fix Suggestion:
Update to version v11.8.4github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.7.0 <v11.7.7Fix Suggestion:
Update to version v11.7.7github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.8.0 <v11.8.4Fix Suggestion:
Update to version v11.8.4Related Resources (3)
Do you need more information?
Contact UsCVSS v4
Base Score:
5.7
Attack Vector
NETWORK
Attack Complexity
HIGH
Attack Requirements
NONE
Privileges Required
HIGH
User Interaction
PASSIVE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
HIGH
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
4.2
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
HIGH
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
NONE
Integrity
HIGH
Availability
NONE
Weakness Type (CWE)
Incorrect Authorization
EPSS
Base Score:
0.15