Privilege Escalation in Mattermost <=11.6.1 via Role Patch API
CVE-2026-6739 Published on June 12, 2026
Mattermost: Delegated admins could patch protected default system roles
Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to require system-level permission when patching protected default system roles, which allows authenticated users with delegated user-management permissions to escalate privileges by altering built-in role permissions via the role patch API.. Mattermost Advisory ID: MMSA-2026-00656
Vulnerability Analysis
CVE-2026-6739 can be exploited with network access, and requires user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality and integrity, and a small impact on availability.
Weakness Type
What is an AuthZ Vulnerability?
The software performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. This allows attackers to bypass intended access restrictions.
CVE-2026-6739 has been classified to as an AuthZ vulnerability or weakness.
Products Associated with CVE-2026-6739
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Affected Versions
Mattermost:- Version 11.6.0, <= 11.6.1 is affected.
- Version 11.5.0, <= 11.5.4 is affected.
- Version 10.11.0, <= 10.11.15 is affected.
- Version 10.11.0, <= 10.11.16 is affected.
- Version 11.7.0 is unaffected.
- Version 11.6.2 is unaffected.
- Version 11.5.5 is unaffected.
- Version 10.11.16 is unaffected.
- Version 10.11.17 is unaffected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.