Saying curse words is assur. <There is more to the sugya than that so don’t just rely on what I said>
But as you said, I don’t think that there is any formal prohibition on hearing or reading curse words.
Inappropriate subjects are also assur to talk about, I believe, but I don’t know if there is a 100% formal prohibition to listen to such things. Can you cite me a source, besides Shulchan Aruch 307:16?