The CookieInterceptor component in Apache Struts before 2.3.1.1 does not use the parameter-name whitelist, which allows remote attackers to execute arbitrary commands via a crafted HTTP Cookie header that triggers Java code execution through a static method.
archives.neohapsis.com/archives/bugtraq/2012-01/0031.html
secunia.com/advisories/47393
struts.apache.org/2.x/docs/s2-008.html
struts.apache.org/2.x/docs/version-notes-2311.html
lists.immunityinc.com/pipermail/dailydave/2012-January/000011.html
www.exploit-db.com/exploits/18329
www.sec-consult.com/files/20120104-0_Apache_Struts2_Multiple_Critical_Vulnerabilities.txt