CVE-2026-3433
Mattermost doesn't restrict role_updated websocket event broadcasts to members of the affected team or channel
Summary
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
Affected packages
| Ecosystem | Package | Affected versions | Fixed versions |
|---|---|---|---|
| Go | github.com/mattermost/mattermost-server | — | 11.6.1, 11.5.5, 10.11.17 |
| Go | github.com/mattermost/mattermost/server/v8 | — | 8.0.0-20260504071740-9408b98025d7 |
Remediation: Upgrade to 11.6.1 or later.
References
Includes data from the GitHub Advisory Database, licensed under CC-BY 4.0.
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EPSS scores provided by the FIRST.org Exploit Prediction Scoring System.