Short answer: don't ask us, ask a lawyer.
Long answer: Noone, not even a lawyer, will be able to give you any sound advice without knowing the specifics of your situation, which include the country you live in. There's no European law that supersedes the law of each state, like Federal Law in the U.S. does, each country is responsible for turning EU directives into country law itself. Details may vary greatly between EU states.
Even if you provided very specific details, we probably couldn't help you, because we're technicians, not lawyers. We can probably help you with producing an exploit; we can't tell you if and where it's legal to publish it.
And even if some of us were lawyers: Imagine we tell you it's ok. You publish your exploit. You get arrested and sued because we were wrong. "I asked some forum guys who seemed highly knowledgable about this" won't help your case at all. If you get a written statement from a lawyer telling you what you're going to do is ok, and he's wrong, your chances are good you'll be able to make him (well, his insurance company) pay for your damages. You won't get anything from us.