Hono is a Web application framework that provides support for any JavaScript runtime. Versions 4.8.0 through 4.9.5 contain a flaw in the getPath utility function which could allow path confusion and potential bypass of proxy-level ACLs (e.g. Nginx location blocks). The original implementation relied on fixed character offsets when parsing request URLs. Under certain malformed absolute-form Request-URIs, this could lead to incorrect path extraction depending on the application and environment. If proxy ACLs are used to protect sensitive endpoints such as /admin, this flaw could have allowed unauthorized access. The confidentiality impact depends on what data is exposed: if sensitive administrative data is exposed, the impact may be high, otherwise it may be moderate. This issue is fixed in version 4.9.6.

Affected: npm: hono

### Summary

A flaw in the `getPath` utility function could allow path confusion and potential bypass of proxy-level ACLs (e.g. Nginx location blocks).

### Details

The original implementation relied on fixed character offsets when parsing request URLs. Under certain malformed absolute-form Request-URIs, this could lead to incorrect path extraction.

Most standards-compliant runtimes and reverse proxies reject such malformed requests with a 400 Bad Request, so the impact depends on the application and environment.

### Impact

If proxy ACLs are used to protect sensitive endpoints such as `/admin`, this flaw could have allowed unauthorized access. The confidentiality impact depends on what data is exposed: if sensitive administrative data is exposed, the impact may be High (CVSS 7.5); otherwise it may be Medium (CVSS 5.3).

### Resolution

The implementation has been updated to correctly locate the first slash after "://", preventing such path confusion.