Is Oracle DBLink Vulnerable?

We have a web page on internet that calls a web service located on our intranet. The web service talks to Database A to get some data. Database A has a DBLink to Database B. This link is used to select data from Database B, but it is not used by the service anyway. However, my boss requested that I remove DBLink and use an alternative because DBLink might be vulnerable. What do you think of that? And what should I do to avoid that vulnerability?