Access Control Flaw in Mattermost Enables Unauthorized Board Admin Privileges
CVE-2026-10527

6.3MEDIUM

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
17 August 2026

What is CVE-2026-10527?

An access control vulnerability exists in Mattermost versions 11.7.x up to 11.7.6, 10.11.x up to 10.11.21, and 11.8.x up to 11.8.3. This vulnerability arises from a failure to properly reconcile SchemeAdmin flags with a user’s current role. Consequently, a user who has been demoted to System Guest may still retain Board Admin privileges, allowing them to carry out administrative actions through the Boards REST API or interface. This can lead to unauthorized modifications and actions within the platform, compromising the integrity of board management.

Affected Version(s)

Mattermost 11.7.0 <= 11.7.6

Mattermost 10.11.0 <= 10.11.21

Mattermost 11.8.0 <= 11.8.3

References

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

CVSS V3.1

Score:
6.3
Severity:
MEDIUM
Confidentiality:
Low
Integrity:
Low
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

ilent0
.