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MEDIUM 6.5

GHSA-9p44-r552-4wp9

Mattermost doesn't sanitize the Remote Cluster API response on PATCH operations

Quick fix

GHSA-9p44-r552-4wp9 — github.com/mattermost/mattermost-server: upgrade to the fixed version with the command below. 

go get github.com/mattermost/mattermost-server@v11.6.1

Details

Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15 fail to sanitize the Remote Cluster API response on PATCH operations, which allows authenticated users with the {{manage_secure_connections}} permission to obtain remote cluster authentication tokens via a PATCH request to the remote cluster endpoint. Mattermost Advisory ID: MMSA-2026-00662

Are you affected?

Enter the version of the package you're using.

Affected packages

Go / github.com/mattermost/mattermost-server
Introduced in: 11.6.0 Fixed in: 11.6.1
Fix go get github.com/mattermost/mattermost-server@v11.6.1
Go / github.com/mattermost/mattermost-server
Introduced in: 11.5.0 Fixed in: 11.5.5
Fix go get github.com/mattermost/mattermost-server@v11.5.5
Go / github.com/mattermost/mattermost-server
Introduced in: 10.11.0 Fixed in: 10.11.16
Fix go get github.com/mattermost/mattermost-server@v10.11.16
Go / github.com/mattermost/mattermost/server/v8
Introduced in: 8.0.0-20250731163400-5b955468ea1e Fixed in: 8.0.0-20260428142921-bd8fc9222672
Fix go get github.com/mattermost/mattermost/server/v8@v8.0.0-20260428142921-bd8fc9222672

References