VDB
KO
MEDIUM 4.3

GHSA-rp4v-qc77-phm4

Mattermost doesn't restrict role_updated websocket event broadcasts to members of the affected team or channel

Quick fix

GHSA-rp4v-qc77-phm4 — 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, 10.11.x <= 10.11.16 fail to restrict role_updated websocket event broadcasts to members of the affected team or channel, which allows an authenticated attacker with guest-level access to observe permission scheme change notifications for private teams they are not a member of via the websocket connection. Mattermost Advisory ID: MMSA-2026-00616

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: 10.11.17
Fix go get github.com/mattermost/mattermost-server@v10.11.17
Go / github.com/mattermost/mattermost/server/v8
Introduced in: 8.0.0-20250731163400-5b955468ea1e Fixed in: 8.0.0-20260504071740-9408b98025d7
Fix go get github.com/mattermost/mattermost/server/v8@v8.0.0-20260504071740-9408b98025d7

References