Improper Handling of URL Encoding (Hex Encoding) Affecting fast-uri package, versions >=2.3.1 <2.4.5>=3.0.0 <3.1.6>=4.0.0 <4.1.3
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.
Do your applications use this vulnerable package?
In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.
Test your applications- Snyk IDSNYK-JS-FASTURI-19256869
- published25 Aug 2026
- disclosed24 Aug 2026
- creditYashvantHange
Introduced: 24 Aug 2026
NewCVE-2026-76172 (opens in a new tab)How to fix?
Upgrade fast-uri to version 2.4.5, 3.1.6, 4.1.3 or higher.
Overview
fast-uri is a Dependency-free RFC 3986 URI toolbox
Affected versions of this package are vulnerable to Improper Handling of URL Encoding (Hex Encoding) through the parseWithStatus, normalizeStringWithStatus, normalizeComparableURI, and resolve paths in index.js. An attacker can steer a URL normalizer or resolver to an attacker-chosen host by supplying a URI whose scheme decodes into reserved delimiter characters, such as %2f%2fevil.example:/pwn, causing normalize() or resolve() to emit a string that reparses with a different authority. This lets untrusted input bypass host-based redirect checks, allowlists, or outbound request decisions when applications trust the normalized result. A scheme containing encoded CRLF can also be serialized back as raw line breaks, which can corrupt a URI placed into a response header.