| Package | Affected versions | Patched versions |
|---|---|---|
| fast-uri | ≥ 2.3.1, < 2.4.5≥ 3.0.0, < 3.1.6≥ 4.0.0, < 4.1.3 | 2.4.53.1.64.1.3 |
| fast-uri | ≥ 2.3.1, < 2.4.5≥ 3.0.0, < 3.1.6≥ 4.0.0, < 4.1.3 | 2.4.53.1.64.1.3 |
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.
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.
None. Upgrade to the patched version.
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