Affected: pyload

pyLoad is a free and open-source download manager written in Python. Prior to version 0.5.0b3.dev97, a Host Header Spoofing vulnerability in the @local_check decorator allows unauthenticated external attackers to bypass local-only restrictions. This grants access to the Click'N'Load API endpoints, enabling attackers to remotely queue arbitrary downloads, leading to Server-Side Request Forgery (SSRF) and Denial of Service (DoS). This issue has been patched in version 0.5.0b3.dev97.

Affected: PyPI: pyload-ng

### Summary

A Host Header Spoofing vulnerability in the `@local_check` decorator allows unauthenticated external attackers to bypass local-only restrictions. This grants access to the Click'N'Load API endpoints, enabling attackers to remotely queue arbitrary downloads, leading to Server-Side Request Forgery (SSRF) and Denial of Service (DoS).

### Details

The `pyload` WebUI provides an API for the Click'N'Load plugin, which is intended to be accessed only from the local machine (e.g., via a browser extension sending requests to `localhost:9666`). To enforce this, the `pyload` application uses a `@local_check` decorator on the relevant routes in `src/pyload/webui/app/blueprints/cnl_blueprint.py`.

However, the `@local_check` implementation relies on the user-controlled `HTTP_HOST` (derived from the HTTP `Host` header) to verify the origin:

```python # src/pyload/webui/app/blueprints/cnl_blueprint.py 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 ```

Because `http_host` is read directly from the `Host` header of the HTTP request, an exter…