A quick search on goggle resulted this hit on stackoverflow which might be helpful:
https://stackoverflow.com/questions/13388069/unexpected-unsupportedoperationexception-on-hibernate-validation-failure

Also this is more of a question rather than a jira bug report which would be more appropriately placed on the forms:
https://discourse.hibernate.org/

Lastly, Hibernate 4.2 is no longer maintained nor supported and I'd consider upgrading to a 5.x release if possible.