Apache Httpd < 2.4.25 : HTTP_PROXY environment variable "httpoxy" mitigation

HTTP_PROXY is a well-defined environment variable in a CGI process, which collided with a number of libraries which failed to avoid colliding with this CGI namespace. A mitigation is provided for the httpd CGI environment to avoid populating the “HTTP_PROXY” variable from a “Proxy:” header, which has never been registered by IANA. This workaround and patch are documented in the ASF Advisory at asf-httpoxy-response.txt and incorporated in the 2.4.25 and 2.2.32 releases. Note: This is not assigned an httpd severity, as it is a defect in other software which overloaded well-established CGI environment variables, and does not reflect an error in HTTP server software.