Bug 2512214 (CVE-2026-71554) - CVE-2026-71554 h2: h2: Request smuggling due to duplicate Host headers
Summary: CVE-2026-71554 h2: h2: Request smuggling due to duplicate Host headers
Keywords:
Status: NEW
Alias: CVE-2026-71554
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-08-06 22:22 UTC by OSIDB Bzimport
Modified: 2026-09-01 10:16 UTC (History)
23 users (show)

Fixed In Version:
Clone Of:
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Description OSIDB Bzimport 2026-08-06 22:22:37 UTC 
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.
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