HTTP Request Smuggling Affecting localstack package, versions <4.14.0-r21
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-CHAINGUARDLATEST-LOCALSTACK-18593787
- published8 Aug 2026
- disclosed6 Aug 2026
Introduced: 6 Aug 2026
NewCVE-2026-71554 (opens in a new tab)How to fix?
Upgrade Chainguard localstack to version 4.14.0-r21 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream localstack package and not the localstack package as distributed by Chainguard.
See How to fix? for Chainguard relevant fixed versions and status.
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.