Our sharing setup is such that Accounts are private OWD and sharing rules are in place for role hierarchy based sharings and no other sharing criteria
Contacts are marked as "Controlled By Parent" - why can one of my users see a contact that is associated with an Account to which he doesn't have access to? (confirmed there is a Insufficient Permissions when he tries to access the account)
Sharing
button to theContact
layout you can see the exact reason.