Mattermost up to 11.4.x Access Control Policy activate cross-site request forgery

Summaryinfo

A vulnerability labeled as problematic has been found in Mattermost up to 10.11.10/11.2.2/11.3.1/11.4.0/11.4.x. Affected is an unknown function of the file /api/v4/access_control_policies/{policy_id}/activate of the component Access Control Policy. Executing a manipulation can lead to cross-site request forgery. This vulnerability is registered as CVE-2026-27659. It is possible to launch the attack remotely. No exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as problematic was found in Mattermost up to 10.11.10/11.2.2/11.3.1/11.4.0/11.4.x. This vulnerability affects an unknown part of the file /api/v4/access_control_policies/{policy_id}/activate of the component Access Control Policy. The manipulation with an unknown input leads to a cross-site request forgery vulnerability. The CWE definition for the vulnerability is CWE-352. The web application does not, or can not, sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted the request. As an impact it is known to affect integrity. CVE summarizes:

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

The weakness was published by Joshua Rogers. The advisory is shared for download at mattermost.com. This vulnerability was named CVE-2026-27659 since 02/23/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available.

Upgrading to version 10.11.11, 11.2.3, 11.3.2, 11.4.1 or 11.5.0 eliminates this vulnerability.

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Productinfo

Type

• Groupware Software

Name

• Mattermost

Version

• 10.11.0
• 10.11.1
• 10.11.2
• 10.11.3
• 10.11.4
• 10.11.5
• 10.11.6
• 10.11.7
• 10.11.8
• 10.11.9
• 10.11.10
• 11.0
• 11.1
• 11.2
• 11.2.0
• 11.2.1
• 11.2.2
• 11.3
• 11.3.0
• 11.3.1
• 11.4
• 11.4.0

License

• open-source

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CPE 2.2info

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