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CVE-2026-27659

MEDIUM CVSS 3.1: 4.6 EPSS 0.02%
Updated Mar 26, 2026
Mattermost
Parameter Value
CVSS 4.6 (MEDIUM)
Affected Versions 10.11.0 — 11.4.1
Fixed In 10.11.11
Type CWE-352 (Cross-Site Request Forgery (CSRF))
Vendor Mattermost
Public PoC No

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

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
Low
Basic privileges needed
User Interaction
Required
User action required

Impact Assessment

Confidentiality
Low
Partial data leak
Integrity
Low
Partial data modification
Availability
None
No disruption

CVSS Vector v3.1

Vulnerable Products 4

Configuration From (including) Up to (excluding)
Mattermost Mattermost_Server
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
10.11.0 10.11.11
Mattermost Mattermost_Server
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
11.2.0 11.2.3
Mattermost Mattermost_Server
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
11.3.0 11.3.2
Mattermost Mattermost_Server
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
11.4.0 11.4.1