CVE-2025-57804
h2 is a pure-Python implementation of a HTTP/2 protocol stack.
Overview
CVE-2025-57804 is a known-severity vulnerability. It was published on August 25, 2025.
Technical 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.
Remediation
Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How CyberStrike helps
Reason, not just scan
It reasons through your app's logic the way a human pentester would, so it finds flaws signature scanners miss.
Learn moreVerified findings
Every finding is proven exploitable before you see it, which cuts the false positives that bury real risk.
Learn moreAI-driven DAST and SAST
Probe running apps and read source from one engine, so issues are caught before and after they ship.
Learn moreOpen source
Read exactly how it tests and what it reports. CyberStrike is open source and in early access.
View the repo
Frequently asked questions
What is CVE-2025-57804?
CVE-2025-57804 is a known-severity vulnerability. It was published on August 25, 2025.
How severe is CVE-2025-57804?
CVSS score information is not yet available for this vulnerability. Check back as the CVE record is updated by NVD analysts.
How do I fix or remediate CVE-2025-57804?
Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2025-57804?
CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2025-57804 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.