I don't know which locale this applies to, but with regular airlines (as opposed to budget airlines, where ticket changes are nigh impossible), I can certainly change and perhaps even cancel my ticket without requiring to communicate the associated confirmation code.
So far, my name and date of travel have been enough to make changes on tickets I've purchased in the past, though sometimes a change incurs a fee.
So, to directly answer your question, you can't, but your question also presumes a certain security related to the confirmation code which isn't there.
Note that I'm not talking about changes through some online system, where typically not the confirmation code, but your login secures access, but simply calling up the airline in question, or visiting one of their offices.