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MEDIUM · 6.7

CVE-2026-6739

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 auth...

Vulnerability Description

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

CVSS Score

6.7

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
LOW

Affected Products

VendorProductVersions
MattermostMattermost Server>= 10.11.0, < 10.11.17

Related Weaknesses (CWE)

CWE-863

References

FAQ

What is CVE-2026-6739?

CVE-2026-6739 is a vulnerability with a CVSS score of 6.7 (MEDIUM). 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 auth...

How severe is CVE-2026-6739?

CVE-2026-6739 has been rated MEDIUM with a CVSS base score of 6.7/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-6739?

Check the references section above for vendor advisories and patch information. Affected products include: Mattermost Mattermost Server.