If an application allows enter an URL in a form field and built-in URLValidator is used, it is possible to prepare a special URL which will be used to overload server process when performing validation of the URL. Solution is to upgrade to Apache Struts version 2.5.12.
https://security.netapp.com/advisory/ntap-20180706-0002/
http://www.securitytracker.com/id/1039114
http://www.securityfocus.com/bid/99563
http://www.oracle.com/technetwork/security-advisory/alert-cve-2017-9805-3889403.html