AIKIDO-2026-793560

TL;DR

The built-in cURL and stream handlers place first-class Proxy-Authorization headers in the origin header list based on Guzzle's proxy prediction rather than the route libcurl actually takes. When a request is sent directly, bypasses the proxy via no-proxy rules, uses a SOCKS proxy, or is redirected into one of those routes, the proxy credential is transmitted to the origin server instead of the proxy. This discloses a private proxy credential to an unintended and possibly attacker-controlled recipient who can then reuse it. The fix keeps managed Proxy-Authorization values out of the origin header list, routes them through libcurl's proxy-only header channel, drops the field on direct and bypassed routes, and rejects values containing CR/LF in the stream handler.