Interpretation Conflict Affecting fast-uri package, versions <2.4.4>=3.0.0 <3.1.5>=4.0.0 <4.1.2
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-18506908
- published2 Aug 2026
- disclosed31 Jul 2026
- creditalanturing881
Introduced: 31 Jul 2026
NewCVE-2026-18446 (opens in a new tab)How to fix?
Upgrade fast-uri to version 2.4.4, 3.1.5, 4.1.2 or higher.
Overview
fast-uri is a Dependency-free RFC 3986 URI toolbox
Affected versions of this package are vulnerable to Interpretation Conflict due to malformed authority introducer handling in parseWithStatus() and resolve() in index.js. An attacker can bypass host-based URL checks and steer requests to an unintended host by supplying a URI that uses \\, /\\, or \\/ in place of // after the scheme. The parser folds those sequences into the path instead of recognizing an authority, while Node’s WHATWG URL treats them as a real authority on special schemes such as http, https, ws, wss, ftp, and file. Applications that validate a URL with fast-uri and then pass the same input to fetch(), undici, or Node’s HTTP clients can be sent to an attacker-controlled destination, enabling SSRF, redirect bypass, or outbound routing abuse.