Apache Struts 2.0.0 through 2.3.4 allows remote attackers to cause a denial of service (CPU consumption) via a long parameter name, which is processed as an OGNL expression.
https://issues.apache.org/jira/browse/WW-3860
https://exchange.xforce.ibmcloud.com/vulnerabilities/78183
http://www.securityfocus.com/bid/55346
http://www.openwall.com/lists/oss-security/2012/09/01/5
http://www.openwall.com/lists/oss-security/2012/09/01/4