Description
PHP through 7.0.8 does not attempt to address RFC 3875 section 4.1.18 namespace conflicts and therefore does not protect applications from the presence of untrusted client data in the HTTP_PROXY environment variable, which might allow remote attackers to redirect an application's outbound HTTP traffic to an arbitrary proxy server via a crafted Proxy header in an HTTP request, as demonstrated by (1) an application that makes a getenv('HTTP_PROXY') call or (2) a CGI configuration of PHP, aka an "httpoxy" issue.
Remediation
References
Related Vulnerabilities
Moodle Numeric Errors Vulnerability (CVE-2011-4305)
PHP Other Vulnerability (CVE-2015-8616)
WordPress Plugin ReviewX-Multi-criteria Rating & Reviews for WooCommerce SQL Injection (1.6.8)
WordPress Plugin WP Like Button Security Bypass (1.6.0)
Moodle Exposure of Sensitive Information to an Unauthorized Actor Vulnerability (CVE-2017-7531)