vLLM: OpenAI auth bypass
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.
Czego dotyczy
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| Platforma | Paczka | Podatne wersje | Poprawka w wersji |
|---|---|---|---|
| Python (PyPI) | vllm | >= 0.3.0, < 0.22.0 | 0.22.0 |
Odnośniki
- https://github.com/vllm-project/vllm/security/advisories/GHSA-94f4-hr76-p5j6
- https://x41-dsec.de/lab/advisories/x41-2026-002-starlette
- https://github.com/vllm-project/vllm/pull/43426
- https://nvd.nist.gov/vuln/detail/CVE-2026-48746
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-48746.json
- https://github.com/vllm-project/vllm
- https://github.com/pypa/advisory-database/tree/main/vulns/vllm/PYSEC-2026-226.yaml
- https://bugzilla.redhat.com/show_bug.cgi?id=2491581
- https://access.redhat.com/security/cve/CVE-2026-48746
- https://access.redhat.com/errata/RHSA-2026:61629
- https://access.redhat.com/errata/RHSA-2026:61627
- https://access.redhat.com/errata/RHSA-2026:43038
- https://access.redhat.com/errata/RHSA-2026:42644
- https://access.redhat.com/errata/RHSA-2026:42142
- https://access.redhat.com/errata/RHSA-2026:42132
- https://access.redhat.com/errata/RHSA-2026:36006
- https://access.redhat.com/errata/RHSA-2026:36005
- https://access.redhat.com/errata/RHSA-2026:30089
- https://access.redhat.com/errata/RHSA-2026:30088
- Wektor CVSS
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H- Słabość (CWE)
CWE-444, CWE-501- Platforma
- Python (PyPI)
- Paczka
vllm- Ujawniono
- 16.06.2026
- Aktualizacja
- 11.10.2026 15:17
Źródła i licencje
OSV / GitHub Advisory Database - PYSEC-2026-226 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-94f4-hr76-p5j6 - CC BY 4.0
Historia podatności: vllm
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