CVE-2026-61599: djust has an unauthenticated arbitrary module import via the WebSocket/SSE view-mount path

The djust live transport resolves the LiveView to mount from a client-supplied dotted path by calling __import__(module_path, ...). The module is imported — running its top-level code (import side effects) — before the framework checks that the resolved object is a LiveView subclass and before any per-view authentication. The LIVEVIEW_ALLOWED_MODULES allowlist that should contain this is fail-open (if allowed_modules: — skipped when the setting is unset, the framework default) and uses loose startswith matching.

An unauthenticated WebSocket client (the WS handshake does not require auth; per-view auth runs only after import + instantiate) can therefore send a mount / live_redirect_mount / url_change frame (or an SSE mount) with view = "<any.importable.module>.AnyName" and cause the server to import — and execute the top-level code of — any importable Python module by name.

Consequences: server-side execution of arbitrary importable modules’ import-time side effects by an unauthenticated client (effectively RCE-by-proxy on any host that has a side-effectful importable module), denial of service (import bombs / expensive dependency trees), and a module/class enumeration oracle via distinct error strings.

Reproduced end-to-end: an unauthenticated WebsocketCommunicator mount frame with the allowlist unset imported and executed a sentinel non-LiveView module before the “not a LiveView subclass” rejection.