Vulnerability DatabaseCVE-2026-9859
Mend.io Vulnerability Database
The largest open source vulnerability database
What is a Vulnerability ID?
New vulnerability? Tell us about it!
CVE-2026-9859
Published:August 17, 2026
Updated:August 31, 2026
Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to enforce PermissionManageBoardRoles on the channelId field of the batch endpoint, which allows an authenticated board editor to relink any board they can edit to an arbitrary channel via a crafted PATCH request. Mattermost Advisory ID: MMSA-2026-00686
Affected Packages
https://github.com/mattermost/mattermost-plugin-boards.git (GITHUB):
Affected version(s) >=v9.0.0 <v9.2.6
Fix Suggestion:
Update to version v9.2.6
github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.7.0 <v11.7.7
Fix Suggestion:
Update to version v11.7.7
github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.8.0 <v11.8.4
Fix Suggestion:
Update to version v11.8.4
github.com/mattermost/mattermost (GO):
Affected version(s) >=v10.11.0 <v10.11.22
Fix Suggestion:
Update to version v10.11.22
Related Resources (3)
https://nvd.nist.gov/vuln/detail/CVE-2026-9859
https://mattermost.com/security-updates
https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/9xxx/CVE-2026-9859.json
Do you need more information?
Contact Us
CVSS v4
Base Score:
7.1
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
LOW
User Interaction
NONE
Vulnerable System Confidentiality
HIGH
Vulnerable System Integrity
NONE
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
6.5
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Weakness Type (CWE)
Incorrect Authorization
CWE-863
EPSS
Base Score:
0.25