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. (CVE-2018-1327)
Impact
There is no impact; F5 products are not affected by this vulnerability.