Inconsistent interpretation of HTTP requests in vLLM - CVE-2026-48746
Published: June 2, 2026
Vulnerability identifier: #VU133252
CSH Severity: High
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
CVE-ID: CVE-2026-48746
CWE-ID: CWE-444
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: vLLM
Affected software:
vLLM
vLLM
Detailed vulnerability description
The vulnerability allows a remote attacker to bypass authentication and use the API without providing a valid API key.
The vulnerability exists due to inconsistent interpretation of HTTP requests in OpenAI API AuthenticationMiddleware when processing requests with a crafted Host header that alters the reconstructed URL path. A remote attacker can send a specially crafted request with invalid characters in the Host header to bypass authentication and use the API without providing a valid API key.
Only instances that use an API key for the OpenAI API and are exposed to attackers are vulnerable. Instances behind an RFC-conforming web server such as nginx are not affected.
How to mitigate CVE-2026-48746
Install security update from vendor's website.