Red Hat Security Advisory 2015-2523-01 – The Apache Commons Collections library provides new interfaces, implementations, and utilities to extend the features of the Java Collections Framework. It was found that the Apache commons-collections library permitted code execution when deserializing objects involving a specially constructed chain of classes. A remote attacker could use this flaw to execute arbitrary code with the permissions of the application using the commons-collections library. With this update, deserialization of certain classes in the commons-collections library is no longer allowed. Applications that require those classes to be deserialized can use the system property “org.apache.commons.collections.enableUnsafeSerialization” to re-enable their deserialization.