AIKIDO-2026-467986

TL;DR

The Bouncy Castle JSSE provider's HTTPS endpoint identification falls back to matching a server certificate's subject common name when the certificate carries no SubjectAltName dNSName entry. This CN fallback is active by default even though it is documented as opt-in, so an unrelated or mis-issued certificate that names the host only in its common name can satisfy hostname verification. A certificate presented over the network can therefore defeat the client's server-identity check and allow the TLS connection to be intercepted. The fix disables the CN fallback by default and gates it behind a dedicated system property.