Threats tagged 'rustsec-2026-0349'

Rustls versions before 0.23.46 have a vulnerability where an unauthenticated ServerHello message can cause the client to downgrade future TLS connections to classical key exchange only, losing post-quantum confidentiality. This occurs because the client records the server-selected key exchange group before server authentication and uses it for future connections. A network attacker can exploit this by responding with a ServerHello selecting a classical group, causing subsequent connections to omit the post-quantum hybrid key exchange. There is no key compromise or authentication bypass. The issue is fixed in Rustls 0.23.46.