CVE-2026-27659 — MEDIUM (4.6)

Q: How severe is CVE-2026-27659?

CVE-2026-27659 has been rated MEDIUM with a CVSS base score of 4.6/10. Review the CVSS metrics above for detailed severity breakdown.

Q: Is there a patch for CVE-2026-27659?

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

Vulnerability Description

Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to properly validate CSRF tokens in the /api/v4/access_control_policies/{policy_id}/activate endpoint, which allows an attacker to trick an admin into changing access control policy active status via a crafted request.. Mattermost Advisory ID: MMSA-2026-00578

CVSS Score

4.6

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

REQUIRED

Scope

UNCHANGED

Confidentiality

LOW

Integrity

LOW

Availability

NONE

Affected Products

Vendor	Product	Versions
Mattermost	Mattermost Server	>= 10.11.0, < 10.11.11

Related Weaknesses (CWE)

CWE-352

References

https://mattermost.com/security-updatesVendor Advisory

FAQ

What is CVE-2026-27659?

CVE-2026-27659 is a vulnerability with a CVSS score of 4.6 (MEDIUM). Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to properly validate CSRF tokens in the /api/v4/access_control_policies/{policy_id}/activate endpoint...

How severe is CVE-2026-27659?

CVE-2026-27659 has been rated MEDIUM with a CVSS base score of 4.6/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-27659?

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