Apple accepts security vulnerability reports via the avenues outlined here. It appears the preferred report mechanism is the web portal, though reports are also accepted to the email product-security@apple.com. You could try those since the "cve@" email does not appear to be working.
cc @mishal_shah would you be the right person to ping about this email (apparently) no longer accepting reports? It's still listed as current on the Swift.org security page.
Does the email address work now? The website says "You’ll receive an email reply from Swift.org to acknowledge that we received your report" but I didn't receive that and also didn't receive a bounce.