CVE-2021-22903

The actionpack ruby gem before 6.1.3.2 suffers from a possible open
redirect vulnerability. Specially crafted Host headers in combination with
certain “allowed host” formats can cause the Host Authorization middleware
in Action Pack to redirect users to a malicious website. This is similar to
CVE-2021-22881. Strings in config.hosts that do not have a leading dot are
converted to regular expressions without proper escaping. This causes, for
example, config.hosts << "sub.example.com" to permit a request with a
Host header value of sub-example.com.

Notes