CVE-2026-16047
Published:August 17, 2026
Updated:September 01, 2026
Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing, or bulk-creating boards with an arbitrary channelId. Mattermost Advisory ID: MMSA-2026-00674
Affected Packages
https://github.com/mattermost/mattermost-plugin-boards.git (GITHUB):
Affected version(s) >=v9.0.0 <v9.2.6Fix Suggestion:
Update to version v9.2.6github.com/mattermost/mattermost (GO):
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) >=v10.11.0 <v10.11.22Fix Suggestion:
Update to version v10.11.22Related 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
LOW
Vulnerable System Integrity
NONE
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
4.3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
LOW
Integrity
NONE
Availability
NONE
Weakness Type (CWE)
Missing Authorization
EPSS
Base Score:
0.16