CVE-2026-76172

### Impact `fast-uri` decodes percent-encoded characters in the scheme component with the legacy global `unescape()` and serializes the result back as raw characters, without re-escaping it or validating it as a scheme. A scheme that decodes to characters outside the RFC 3986 scheme grammar can therefore introduce structure the original input did not contain. For example, `%2f%2fevil.example:/pwn` parses with no authority (`parse().host` is `undefined`), but `resolve()` and `normalize()` return `//evil.example:/pwn`, which reparses with host `evil.example`. The `%uXXXX` form (`%u002f%u002fevil.example:/pwn`) produces the same result, and a scheme containing `%0d%0a` reaches the output as a raw CR LF. Applications that normalize or resolve untrusted URLs before a redirect check, host allowlist, or outbound request decision, especially ones that treat a missing authority as same-origin, can be steered to an attacker-chosen authority, and a normalized URI placed in a response header can carry an injected CR LF. ### Patches Upgrade to `fast-uri` >= 4.1.3, or >= 3.1.6 in the v3.x release line, or >= 2.4.5 in the v2.x release line. ### Workarounds None. Upgrade to the patched version.