CookieInterceptor in Apache Struts 2.x before 2.3.20, when a wildcard cookiesName value is used, does not properly restrict access to the getClass method, which allows remote attackers to "manipulate" the ClassLoader and modify session state via a crafted request. NOTE: this vulnerability exists because of an incomplete fix for CVE-2014-0113.
http://www.securityfocus.com/bid/67218
http://www.oracle.com/technetwork/topics/security/cpuapr2015-2365600.html
http://www.huawei.com/en/security/psirt/security-bulletins/security-advisories/hw-350733.htm