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CVE-2026-71554 Details

ANALYZED

This CVE record has been analyzed and enriched by NVDAPI.com as an independent party.

Description

h2 is a pure-Python implementation of a HTTP/2 protocol stack. Versions up to and including 4.4.0 accept request header blocks containing more than one Host header, and forward every Host header to the consuming application. Where the consumer downgrades HTTP/2 to HTTP/1.1, the resulting request carries two Host header lines, providing a request smuggling primitive. This issue is fixed in version 4.4.1.

Metrics

CVSS 3.x Severity and Vector Strings:

VolerionCVSS-B:3.7 LOWVector:CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

CNA: [email protected]CVSS-B:5.3 MEDIUMVector:CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://github.com/python-hyper/h2/commit/292a40829feefda98c8509dcdbbb4a57af9bd6a6	[email protected]	Source CodeVendor
https://github.com/python-hyper/h2/security/advisories/GHSA-6hr6-w5qg-qmwg	[email protected]	AdvisoryRemedyVendor

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-444	Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')	[email protected]

Affected Products

Product	Versions
h2	<= 4.4.0 (semver)
CPE No CPEs found in CPE dictionary for this product. Remediation Upgrade: 4.4.1moderate effort Mitigation:low effort Follow HTTP semantics best practices in your application code.

Change History

2 change records found show changes

Date	Action	Recorded By
Aug 8, 2026	CVE Modified	CISA-ADP
Aug 6, 2026	New CVE Received	[email protected]