CVE-2026-123611 rustls before 0.23.46 Key Exchange Downgrade via Unauthenticated ServerHello

rustls before 0.23.46 contains a key exchange downgrade vulnerability that allows network attackers to poison the per-server-name key-exchange group record via an unauthenticated ServerHello. Attackers can answer one connection with a ServerHello selecting X25519, causing later ClientHellos to se...