Inconsistent interpretation of HTTP requests in h11 - CVE-2025-43859
Published: May 2, 2025
Vulnerability identifier: #VU108124
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: CVE-2025-43859
CWE-ID: CWE-444
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Hyper
Affected software:
h11
h11
Detailed vulnerability description
The vulnerability allows a remote attacker to perform HTTP request smuggling attacks.
The vulnerability exists due to improper validation of HTTP requests in h11/_readers.py. A remote attacker can send a specially crafted HTTP request to the server and smuggle arbitrary HTTP headers.
Successful exploitation of vulnerability may allow an attacker to poison HTTP cache and perform phishing attacks.
How to mitigate CVE-2025-43859
Install updates from vendor's website.