CVE-2018-14773

An issue was discovered in Http Foundation in Symfony 2.7.0 through 2.7.48,
2.8.0 through 2.8.43, 3.3.0 through 3.3.17, 3.4.0 through 3.4.13, 4.0.0
through 4.0.13, and 4.1.0 through 4.1.2. It arises from support for a
(legacy) IIS header that lets users override the path in the request URL
via the X-Original-URL or X-Rewrite-URL HTTP request header. These headers
are designed for IIS support, but it’s not verified that the server is in
fact running IIS, which means anybody who can send these requests to an
application can trigger this. This affects
\Symfony\Component\HttpFoundation\Request::prepareRequestUri() where
X-Original-URL and X_REWRITE_URL are both used. The fix drops support for
these methods so that they cannot be used as attack vectors such as web
cache poisoning.