Scott Geary of VendHQ discovered that the Apache HTTPD server used the
value of the Proxy header from HTTP requests to initialize the
HTTP_PROXY environment variable for CGI scripts, which in turn was
incorrectly used by certain HTTP client implementations to configure the
proxy for outgoing HTTP requests. A remote attacker could possibly use
this flaw to redirect HTTP requests performed by a CGI script to an
attacker-controlled proxy via a malicious HTTP request.