Input validation error in starlette - #VU132131
Published: May 22, 2026
Vulnerability identifier: #VU132131
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: N/A
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Encode
Affected software:
starlette
starlette
Detailed vulnerability description
The vulnerability allows a remote attacker to bypass path-based security checks.
The vulnerability exists due to improper input validation in request.url reconstruction when processing a malformed Host header. A remote attacker can send a specially crafted Host header to bypass path-based security checks.
The issue occurs because routing uses the raw HTTP path while security-sensitive code may rely on request.url.path reconstructed from the Host header.
Remediation
Install security update from vendor's website.