CVE-2026-27659

Name: CVE-2026-27659
Creator: NVD / NIST
Published: 2026-03-25T17:16:56.977+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.6/10EPSS 0.12%

Last modified Jun 17, 2026

CVE-2026-27659 is a medium-severity vulnerability rated 4.6/10 on the CVSS scale. 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. EPSS estimates a 0.12% chance of exploitation in the next 30 days.

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

Metrics

CVSS 3.1

4.6/10

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

EPSS Probability

0.12%

2.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-352

Affected Software

Vendor	Product	Versions
Mattermost	Mattermost Server	>= 10.11.0, < 10.11.11
Mattermost	Mattermost Server	>= 11.2.0, < 11.2.3
Mattermost	Mattermost Server	>= 11.3.0, < 11.3.2
Mattermost	Mattermost Server	>= 11.4.0, < 11.4.1

References

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

Timeline

Published: Mar 25, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-27659?

How severe is CVE-2026-27659?

CVE-2026-27659 has a CVSS score of 4.6/10 (MEDIUM severity). The EPSS model estimates a 0.12% probability of exploitation in the next 30 days.

How do I fix CVE-2026-27659?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-27659?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST