GHSA-vfm6-r2gc-pwww: Symfony2 security issue when the trust proxy mode is enabled

An application is vulnerable if it uses the client IP address as returned by the Request::getClientIp() method for sensitive decisions like IP based access control.

To fix this security issue, the following changes have been made to all versions of Symfony2:

A new Request::setTrustedProxies() method has been introduced and should be used intead of Request::trustProxyData() to enable the trust proxy mode. It takes an array of trusted proxy IP addresses as its argument:

// before (probably in your front controller script)
Request::trustProxyData();

// after
Request::setTrustedProxies(array('1.1.1.1'));
// 1.1.1.1 being the IP address of a trusted reverse proxy

The Request::trustProxyData() method has been deprecated (when used, it automatically trusts the latest proxy in the chain -- which is the current remote address):

Request::trustProxyData();

// is equivalent to
Request::setTrustedProxies(array($request->server->get('REMOTE_ADDR')));

We encourage all Symfony2 users to upgrade as soon as possible. It you don't want to upgrade to the latest version yet, you can also apply the following patches:

• Patch for Symfony 2.0.19
• Patch for Symfony 2.1.4