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CVE-2025-57804
Good to know:
Date: August 25, 2025
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.
Severity Score
Related Resources (6)
Severity Score
Weakness Type (CWE)
Improper Neutralization of CRLF Sequences ('CRLF Injection')
CWE-93Top Fix
Upgrade Version
Upgrade to version h2 - 4.3.0;https://github.com/python-hyper/h2.git - v4.3.0
CVSS v3.1
| Base Score: |
|
|---|---|
| Attack Vector (AV): | NETWORK |
| Attack Complexity (AC): | LOW |
| Privileges Required (PR): | NONE |
| User Interaction (UI): | NONE |
| Scope (S): | CHANGED |
| Confidentiality (C): | LOW |
| Integrity (I): | LOW |
| Availability (A): | NONE |