HTTP Request Smuggling Affecting undici package, versions <6.28.0>=7.0.0 <7.29.0>=8.0.0 <8.9.0
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-UNDICI-18426063
- published30 Jul 2026
- disclosed29 Jul 2026
- creditUnknown
Introduced: 29 Jul 2026
NewCVE-2026-16728 (opens in a new tab)How to fix?
Upgrade undici to version 6.28.0, 7.29.0, 8.9.0 or higher.
Overview
undici is an An HTTP/1.1 client, written from scratch for Node.js
Affected versions of this package are vulnerable to HTTP Request Smuggling due to the interceptors.retry() flow in lib/handler/retry-handler.js. An attacker can cause a proxy or gateway that forwards Undici responses to emit a body whose length does not match the Content-Length header by sending a partial 206 response with mismatched framing and closing the connection to trigger a retry or resume. This can corrupt downstream HTTP framing, causing client or intermediary hangs and response parsing errors, and can expose users of the forwarding service to broken responses or connection desynchronization.