HTTP Request Smuggling Affecting h3 package, versions <1.15.5
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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Test your applications- Snyk IDSNYK-JS-H3-15010914
- published16 Jan 2026
- disclosed15 Jan 2026
- creditSimon Köck
Introduced: 15 Jan 2026
CVE-2026-23527 (opens in a new tab)How to fix?
Upgrade h3 to version 1.15.5 or higher.
Overview
h3 is a Minimal H(TTP) framework built for high performance and portability.
Affected versions of this package are vulnerable to HTTP Request Smuggling via improper parsing of the Transfer-Encoding header in the readRawBody() function. An attacker can bypass security controls and poison web caches by sending specially crafted HTTP requests with case-variant headers.