Improper Encoding or Escaping of Output Affecting fast-uri package, versions <2.4.6>=3.0.0 <3.1.7>=4.0.0 <4.1.4
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-FASTURI-19502739
- published3 Sept 2026
- disclosed2 Sept 2026
- creditYashvant Mahadev Hange
Introduced: 2 Sep 2026
NewCVE-2026-84292 (opens in a new tab)How to fix?
Upgrade fast-uri to version 2.4.6, 3.1.7, 4.1.4 or higher.
Overview
fast-uri is a Dependency-free RFC 3986 URI toolbox
Affected versions of this package are vulnerable to Improper Encoding or Escaping of Output that enables authority injection in the recomposeAuthority function, which escapes the userinfo and host components but concatenates the port field verbatim, so non-digit characters in the port introduce authority delimiters. An attacker can restructure the URI to redirect requests to a server they control by supplying a port value such as @127.0.0.1:8124, which demotes the legitimate host to userinfo and yields http://trusted.example:@127.0.0.1:8124/app. This requires the application to build URIs from separate components and assign untrusted data directly to the port field of an object passed to serialize(), normalize(), or equal(), and ports obtained via parse() are unaffected because parsing validates digit-only values.