Summary

A pathname parsing discrepancy in srvx's FastURL allows middleware bypass on the Node.js adapter when a raw HTTP request uses an absolute URI with a non-standard scheme (e.g. file://).

Details

When Node.js receives an absolute URI in the request line (e.g. GET file://hehe?/internal/run HTTP/1.1), req.url is set verbatim to file://hehe?/internal/run. Since this doesn't start with /, NodeRequestURL passes it directly to FastURL as a string, which stores it in #href for lazy manual parsing.

FastURL#getPos() locates the pathname by finding :// then scanning for the next / — but this fails for URLs like file://hehe?/internal/run where a ? appears before the first / after the authority. The manual parser extracts pathname as /internal/run, while native URL correctly parses it as pathname / with search ?/internal/run.

This discrepancy means the router (using the fast-path) matches /internal/run, but if any middleware triggers a deopt to native URL (e.g. by accessing hostname), subsequent middleware sees a different pathname — bypassing route-based middleware guards.

This is a bypass of CVE-2026-33131.

Impact

Route-based middleware (auth guards, rate limiters, etc.) can be bypassed on the Node.js adapter when a prior middleware triggers FastURL deopt. Requires sending a raw HTTP request (not possible from browsers).

Fix

srvx FastURL constructor now deopts to native URL for any string not starting with /, ensuring consistent pathname resolution.