Access Control Flaw in Mattermost Messaging Platform
CVE-2026-6062

6.4MEDIUM

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
22 June 2026

What is CVE-2026-6062?

A significant access control vulnerability in Mattermost allows authenticated users to manipulate channel subscriptions. Specifically, versions of Mattermost prior to 11.7.0, 11.6.2, 11.5.5, and 10.11.17 fail to adequately validate channel ownership before applying edits to subscriptions. This flaw enables an attacker to hijack subscriptions from channels they are not authorized to access by sending a crafted PUT request to the subscription edit endpoint, posing serious risks to user confidentiality and data integrity.

Affected Version(s)

Mattermost 11.7.0

Mattermost 11.6.0 <= 11.6.2

Mattermost 11.5.0 <= 11.5.5

References

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

CVSS V3.1

Score:
6.4
Severity:
MEDIUM
Confidentiality:
High
Integrity:
Low
Availability:
High
Attack Vector:
Network
Attack Complexity:
High
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

0hmz
.