GHSA-x698-5hjm-w2m5 pyLoad is vulnerable to attacks that bypass localhost restrictions, enabling the creation of arbitrary packages

• PyPI pyload-ng: <= 0.5.0b3.dev88 (no fix yet)

Summary Any unauthenticated attacker can bypass the localhost restrictions posed by the application and utilize this to create arbitrary packages. Details Any unauthenticated attacker can bypass the localhost restrictions posed by the application and utilize this to create arbitrary packages. This is done by changing the `Host` header to the value of `127.0.0.1:9666`. PoC The application has middleware that prevents access to several routes by checking whether the `Host` header has a specific value. We bypassed this restriction. https://github.com/pyload/pyload/blob/4159a1191ec4fe6d927e57a9c4bb8f54e16c381d/src/pyload/webui/app/blueprints/cnl_blueprint.py#L21-L36 ```python : decorator def local_check(func): @wraps(func) def wrapper(*args, **kwargs): remote_addr = flask.request.environ.get("REMOTE_ADDR", "0") http_host = flask.request.environ.get("HTTP_HOST", "0") if remote_addr in ("127.0.0.1", "::ffff:127.0.0.1", "::1", "localhost") or http_host in ( "127.0.0.1:9666", "[::1]:9666", ): return func(*args, **kwargs) else: return "Forbidden", 403 return wrapper ``` Below we see that the '/flash/add' endpoint uses the middleware above. https://github.com/pyload/pyload/blob/4159a1191ec4fe6d927e57a9c4bb8f54e16c381d/src/pyload/webui/app/blueprints/cnl_blueprint.py#L56-L58C11 ```python @bp.route("/flash/add", methods=["POST"], endpoint="add") @local_check def add(): ``` Notice how we are not authorized to access this endpoint when sending a request. However, if we set the `Host` header to be `127.0.0.1:9666`, we notice the request returns `success`. Checking the front end as an admin, we now see that this did indeed succeed. Impact An unauthenticated user can perform actions that should only be available to authenticated users.