Unless you already have a confidentially agreement in place, your current boss did nothing legally wrong about calling your former boss; the law does not prevent person A from complaining to person B about person C in the absence of a contractual obligation to not do so. And if there is currently no confidentiality agreement in place, then the company does not face any obligations or liability to you because your boss called another person to discuss you; that is, agreements cannot be "broken" before they exist.Note that while your current boss may complain about you to others, including a former boss with a high opinion of you, he may not defame you. Defamation is the knowing making of false statements of fact whcih damage another's reputation. So if you current boss only expressed opinions (such as "I think John/Jane Doe is lazy," or "John/Jane Doe is bad worker") or stated true facts (such as saying you had often been late to work, when that is true), then that would not be defamation; but if he said untrue negative facts about you (such as saying that you had stolen from the company, when you did not), that may be defamation and you may have a legal cause of action.