HTTP Request Smuggling Affecting h2 package, versions [,4.4.1)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published8 Aug 2026
- disclosed6 Aug 2026
- creditSunandM
Introduced: 6 Aug 2026
NewCVE-2026-71554 (opens in a new tab)How to fix?
Upgrade h2 to version 4.4.1 or higher.
Overview
h2 is a Pure-Python HTTP/2 protocol implementation
Affected versions of this package are vulnerable to HTTP Request Smuggling via the processing of HTTP/2 request headers containing multiple Host headers. An attacker can interfere with downstream HTTP/1.1 applications by crafting requests that result in multiple Host headers being forwarded, potentially enabling request smuggling attacks.