Migration documentation for moving from Hibernate 4.3 to Hibernate 5.0, is described here..

That may be helpful in getting started. I don't see a similar description of how to migrate from Hibernate 4.2 to 4.3, which is a big jump (JPA 2.0 to 2.1). hibernate-dev@lists.jboss.org may be a good place to ask about migrating from 4.2 to 4.3.

This jira should cover migrating native Hibernate applications as well as JPA applications.