CVE-2026-123867: Node.js is vulnerable to a per-host mTLS authorization bypass via a CA-only SNI context failing open to the default CA

A per-host mutual-TLS authorization bypass in Node.js lets a client authorized for the default hostname reach a protected hostname it is not authorized for. When a TLS server assigns a hostname a different client-certificate CA with server.addContext(host, { ca: protectedCA }) but no server certificate in that SNI context, the per-host client CA is never installed and the handshake falls back to the default client CA. In src/crypto/cryptotls.cc, CertCbDone installs the SNI context's CA only when setSniContext succeeds, but setSniContext returns false for a context with no server certificate, so a CA-only SNI context silently keeps the default CA. A client holding a certificate trusted by the default CA, but not the protected CA, can therefore complete mTLS to the protected hostname and read its response even with requestCert and rejectUnauthorized enabled, while a client certified by the protected CA is rejected.