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Protecting Struts 2 from OGNL Related Attacks by Using Servlet Filter

Apache Struts 2 is an open-source web application framework which is widely used all over the world. Recently, some vulnerabilities leveraging Object Graph Navigation Language (OGNL) used in Struts 2 that allow remote code execution are reported. Protecting Struts 2 applications is not easy, because it needs some time to apply security updates and attacks can start shortly after vulnerabilities are published. Many cases of attacks leveraging Struts 2 vulnerabilities have been observed. In addition, it is difficult to alter existing system structures or conduct additional development. In this paper, we propose a method for protection against attacks leveraging OGNL by using Servlet Filter which can block specific patterns of parameters without change of existing system structures or programs.