CVE-2011-1498: Exposure of Sensitive Information to an Unauthorized Actor in Apache HttpClient

The vulnerability stems from the RequestProxyAuthentication class's process method handling proxy authentication headers. The commit diff shows a critical addition of a route.isTunnelled() check to prevent Proxy-Authorization headers from being sent to the origin server during tunneling. Before this fix, the absence of this check allowed the header to leak. The function's responsibility for proxy authentication logic and the explicit patch to add tunneling validation directly correlate to the vulnerability description.