The Apache Struts REST Plugin is using XStream library which is vulnerable and allow perform a DoS attack when using a malicious request with specially crafted XML payload. Upgrade to the Apache Struts version 2.5.16 and switch to an optional Jackson XML handler as described here http://struts.apache.org/plugins/rest/#custom-contenttypehandlers. Another option is to implement a custom XML handler based on the Jackson XML handler from the Apache Struts 2.5.16.
The TextParseUtil.translateVariables method in Apache Struts 2.x before 2.3.20 allows remote attackers to execute arbitrary code via a crafted OGNL expression with ANTLR tooling.
Apache Struts 2.x before 2.3.29 allows remote attackers to execute arbitrary code via a "%{}" sequence in a tag attribute, aka forced double OGNL evaluation. NOTE: this vulnerability exists because of an incomplete fix for CVE-2016-0785.
The REST Plugin in Apache Struts 2.1.1 through 2.3.x before 2.3.34 and 2.5.x before 2.5.13 uses an XStreamHandler with an instance of XStream for deserialization without any type filtering, which can lead to Remote Code Execution when deserializing XML payloads.
Cross-site scripting (XSS) vulnerability in the URLDecoder function in JRE before 1.8, as used in Apache Struts 2.x before 2.3.28, when using a single byte page encoding, allows remote attackers to inject arbitrary web script or HTML via multi-byte characters in a url-encoded parameter.
Apache Struts 2.x before 2.3.28 allows remote attackers to execute arbitrary code via a "%{}" sequence in a tag attribute, aka forced double OGNL evaluation.
ParametersInterceptor in Apache Struts before 2.3.20 does not properly restrict access to the getClass method, which allows remote attackers to "manipulate" the ClassLoader and execute arbitrary code via a crafted request. NOTE: this vulnerability exists because of an incomplete fix for CVE-2014-0094.
CookieInterceptor in Apache Struts 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 execute arbitrary code via a crafted request. NOTE: this vulnerability exists because of an incomplete fix for CVE-2014-0094.
The ParametersInterceptor in Apache Struts before 2.3.16.2 allows remote attackers to "manipulate" the ClassLoader via the class parameter, which is passed to the getClass method.