CVE-2025-57804

MEDIUM EPSS 72.9%
Published Aug 25, 202510mo ago · Modified Jun 17, 20262w ago
6.9 CVSS 4.0
Medium
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Published Aug 25, 2025 10mo ago
Last Modified Jun 17, 2026 2w ago

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.

CVSS Details

Base Score
6.9
Exploitability
—
Impact
—
Vector string
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope X

Threat Intelligence

EPSS Exploit Probability
72.9% percentile
Exploit & Patch Status
No Known Exploit
No Patch Available

Weaknesses 1

CWE-93

References 3

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

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.