CVE-2025-57804

Description

h2 is a pure-Python implementation of a HTTP/2 protocol stack. Prior to version 4.3.0, an HTTP/2 request splitting vulnerability allows attackers to perform request smuggling attacks by injecting CRLF characters into headers. This occurs when servers downgrade HTTP/2 requests to HTTP/1.1 without properly validating header names/values, enabling attackers to manipulate request boundaries and bypass security controls. This issue has been patched in version 4.3.0.

Weakness Type (CWE)

CWE-93 CWE-93

References

Other References

https://github.com/python-hyper/h2/commit/035e9899f95e3709af098f578bfc3cd302298e3a https://github.com/python-hyper/h2/security/advisories/GHSA-847f-9342-265h https://lists.debian.org/debian-lts-announce/2025/09/msg00004.html

Frequently Asked Questions

What is CVE-2025-57804? +

h2 is a pure-Python implementation of a HTTP/2 protocol stack. Prior to version 4.3.0, an HTTP/2 request splitting vulnerability allows attackers to perform request smuggling attacks by injecting CRLF characters into headers. This occurs when servers downgrade HTTP/2 requests to HTTP/1.1 without properly validating header names/values, enabling attackers to manipulate request boundaries and bypass security controls. This issue has been patched in version 4.3.0.

How do I check if I'm vulnerable to CVE-2025-57804? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2025-53094

ESPAsyncWebServer is an asynchronous HTTP and WebSocket server library for ESP32, ESP8266, RP2040 and RP2350. In versions up to and …

CVE-2024-51501

Refit is an automatic type-safe REST library for .NET Core, Xamarin and .NET The various header-related Refit attributes (Header, HeaderCollection …

CVE-2025-52479

HTTP.jl provides HTTP client and server functionality for Julia, and URIs.jl parses and works with Uniform Resource Identifiers (URIs). URIs.jl …

CVE-2025-40671

SQL injection vulnerability in AES Multimedia's Gestnet v1.07. This vulnerability allows an attacker to retrieve, create, update and delete databases …

CVE-2024-36459

A CRLF cross-site scripting vulnerability has been identified in certain configurations of the SiteMinder Web Agent for IIS Web Server …

CVE-2025-59419

Netty is an asynchronous, event-driven network application framework. In versions prior to 4.1.128.Final and 4.2.7.Final, the SMTP codec in Netty …