CVE-2026-48746

Ein entfernter, anonymer Angreifer kann eine Schwachstelle in vllm ausnutzen, um Sicherheitsvorkehrungen zu umgehen.

### Summary A vulnerability in ASGI web servers and starlette's trust on those web servers enables an authentication bypass of the OpenAI API `AuthenticationMiddleware`, which was discovered during @x41sec's source code audit. It allows to use the API without providing the configured `VLLM_API_KEY` or `--api-key`. ### Details In https://github.com/vllm-project/vllm/blob/v0.14.0/vllm/entrypoints/openai/api_server.py#L689-L692 the `url_path` is taken from the `URL`, which is reconstructed by _starlette_ based on the request `scope`. ```py from starlette.datastructures import URL, Headers, MutableHeaders, State # ... url_path = URL(scope=scope).path.removeprefix(root_path) headers = Headers(scope=scope) if url_path.startswith("/v1") and not self.verify_token(headers): response = JSONResponse(content={"error": "Unauthorized"}, status_code=401) return response(scope, receive, send) return self.app(scope, receive, send) ``` The request `scope` includes the request's `Host:` header and reconstructs the URL as shown below: ```py f"{scheme}://{host_header}{path}" ``` Neither starlette nor [any of the ASGI servers](https://asgi.readthedocs.io/en/latest/implementations.html#servers) (including uvicorn, which vllm uses) properly filter the `Host:` header for invalid characters. This allows an attacker to include special URL characters such as `/` or `?` in the `Host:` header and thereby control the reconstructed URL and it's `.path` attribute. FastAPI/starlette's routing uses the HTTP path and does not depend on the parsed url.path attribute, allowing attackers to reach an endpoint via a certain path while providing a different value in the `.path`. ### Impact - Instances of vllm that use an API Key for the OpenAI API and expose the API to attackers. - Instances behind an RFC-conforming web server (such as nginx) are **not** affected.

vLLM is an inference and serving engine for large language models (LLMs). From 0.3.0 until 0.22.0, a vulnerability in ASGI web servers and starlette's trust on those web servers enables an authentication bypass of the OpenAI API AuthenticationMiddleware. It allows to use the API without providing the configured VLLM_API_KEY or --api-key. This vulnerability is fixed in 0.22.0.