Is CVE-2026-27659 actively exploited?

CVE-2026-27659 has no public evidence of in-the-wild exploitation as of 2026-03-26.

What is the CVSS score for CVE-2026-27659?

CVE-2026-27659 has a CVSS score of 4.6 (MEDIUM severity). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N.

How do I patch CVE-2026-27659?

Patch guidance is available from mattermost security advisories. CVEDatabase generates AI-assisted remediation guidance on demand for CVE-2026-27659.

CVE-2026-27659 - remediation guidance & executive summary

Q: Which products are affected by CVE-2026-27659?

4 products: mattermost mattermost server, mattermost mattermost server, mattermost mattermost server, mattermost mattermost server.

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 Metrics

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N
Attack Vector: network
Complexity: low
Privileges: low
User Action: required
Scope: unchanged
Confidentiality: low
Integrity: low
Availability: none
Weaknesses: CWE-352 · Cross-Site Request Forgery

Metadata

Primary Vendor: MATTERMOST
Published: 3/25/2026
Last Modified: 3/26/2026
Source: NIST NVD
Note: Verify all details with official vendor sources before applying patches.

Affected Products

mattermost : mattermost_servermattermost : mattermost_servermattermost : mattermost_servermattermost : mattermost_server

Remediation Guidance

Executive Summary

Cite this page

CVE-2026-27659. CVEDatabase.com. Retrieved 1 May 2026. https://cvedatabase.com/cve/CVE-2026-27659

View on NIST NVD

CVE-2026-27659 vulnerability