fast-uri vulnerable to host confusion via percent-encoded authority delimiters

Open Source Vulnerabilities CVE-2026-6322

fast-uri normalize() decoded percent-encoded authority delimiters inside the host component and then re-emitted them as raw delimiters during serialization. A host that combined an allowed domain, an encoded at-sign, and a different domain was re-emitted with the at-sign as a raw userinfo separator, changing the URI's authority to the second domain. Applications that normalize untrusted URLs before host allowlist checks, redirect validation, or outbound request routing can be steered to a different authority than the input appeared to specify. Versions <= 3.1.1 are affected. Update to 3.1.2 or later.

Open Source Vulnerabilities GHSA-v39h-62p7-jpjc

### Impact `fast-uri` v3.1.1 and earlier decodes percent-encoded authority delimiters (`%40` as `@`, `%3A` as `:`) inside the host component and serializes them back as raw characters. This changes the URI structure, turning a hostname into userinfo plus a different host. For example, `http://trusted.com%40evil.com/` normalizes to `http://[email protected]/`, which reparses as host `evil.com` with userinfo `trusted.com`. Applications that normalize untrusted URLs before host allowlist checks, redirect validation, or outbound request routing can be steered to a different authority than the original URL appeared to contain. ### Patches Upgrade to `fast-uri` >= 3.1.2, or if you are in the v2.x release line, v2.4.1 ### Workarounds None. Upgrade to the patched version.