CVE-2026-55571: djust authentication bypass: a login_required / on_mount LiveView mount redirect does not close the WebSocket, allowing an unauthenticated client to dispatch event-handler calls

djust’s LiveViewConsumer mounts a LiveView over a WebSocket. When a view is gated (login_required / permission_required, or an on_mount hook that returns a redirect) and the connecting user is not authorized, the consumer sent the client a {"type":"navigate","to":...} redirect frame and then returned — without closing the socket and without clearing self.view_instance. Only the PermissionDenied branch closed the connection (close(4403)).

A real browser obeys the navigate frame and leaves, hiding the problem. A raw WebSocket client that ignores the redirect keeps an open, mounted socket. Because handle_event did not re-check authentication/authorization after mount, that client could then send {"type":"event", ...} frames and invoke any @event_handler method on the gated view with no authenticated session — an authentication bypass on the live mutation path.

Who is affected: apps that expose LiveViews gated by login_required / permission_required / a redirecting on_mount hook, where the gated view’s event handlers perform sensitive reads or mutations and do not independently re-verify the user. Exploitation requires a non-browser WebSocket client and knowledge (or enumeration) of the view path and event names.