A vulnerability was found in a previous version of mod_auth_mellon. An open redirect in the logout URL allows requests with backslashes to pass through by assuming that it is a relative URL, while the browsers silently convert backslash characters into forward slashes treating them as an absolute URL. This mismatch allows an attacker to bypass the redirect URL validation logic in apr_uri_parse function.A vulnerability was found in mod_auth_mellon. If Apache is configured as a reverse proxy and mod_auth_mellon is configured to only let through authenticated users , adding special HTTP headers that are normally used to start the special SAML ECP can be used to bypass authentication.