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
{
"cwe_ids": [
"CWE-200"
],
"github_reviewed": true,
"github_reviewed_at": "2026-08-24T21:30:50Z",
"nvd_published_at": "2026-06-12T17:16:22Z",
"severity": "MODERATE"
}