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GHSA-94f4-hr76-p5j6
No affected components available
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.
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:
f"{scheme}://{host_header}{path}"
Neither starlette nor any of the ASGI 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.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a high impact on the availability of the system.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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