httpoxy – a CGI application vulnerability for PHP, Go, Python and others

httpoxy is a set of vulnerabilities that affect application code running in CGI, or CGI-like environments.

It comes down to a simple namespace conflict:

• RFC 3875 (CGI) puts the HTTP Proxy header from a request into the environment variables as HTTP_PROXY
• HTTP_PROXY is a popular environment variable used to configure an outgoing proxy

This leads to a remotely exploitable vulnerability. If you’re running PHP or CGI, you should block the Proxy header now.