CVE-2026-123867

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/crypto_tls.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. This vulnerability affects Node.js 26.x, 24.x, and 22.x.