Version Details and Security Vulnerabilities

Summary

By sending a crafted HTTP request to a server behind an CDN, it is possible in some circumstances to poison the CDN cache and highly impacts the availability of a site.

It is possible to craft a request, such as https://mysite.com/?/_payload.json which will be rendered as JSON. If the CDN in front of a Nuxt site ignores the query string when determining whether to cache a route, then this JSON response could be served to future visitors to the site.

Impact

An attacker can perform this attack to a vulnerable site in order to make a site unavailable indefinitely. It is also possible in the case where the cache will be reset to make a small script to send a request each X seconds (=caching duration) so that the cache is permanently poisoned making the site completely unavailable.

Conclusion :

This is similar to a vulnerability in Next.js that resulted in CVE-2024-46982 (and see this article, in particular the "Internal URL parameter and pageProps" part, the latter being very similar to the one concerning us here.)

Summary

A client-side path traversal vulnerability in Nuxt's Island payload revival mechanism allowed attackers to manipulate client-side requests to different endpoints within the same application domain when specific prerendering conditions are met.

Technical Details

The vulnerability occurs in the client-side payload revival process (revive-payload.client.ts) where Nuxt Islands are automatically fetched when encountering serialized __nuxt_island objects. The issue affects the following flow:

1. During prerendering, if an API endpoint returns user-controlled data containing a crafted __nuxt_island object
2. This data gets serialized with devalue.stringify and stored in the prerendered page
3. When a client navigates to the prerendered page, devalue.parse deserializes the payload
4. The Island reviver attempts to fetch /__nuxt_island/${key}.json where key could contain path traversal sequences

Prerequisites for Exploitation

This vulnerability requires all of the following conditions:

1. Prerendered pages: The application must use Nuxt's prerendering feature (nitro.prerender)
2. Attacker-controlled API responses: The attacker must be able to control the response content of an API endpoint that is called during prerendering via useFetch, useAsyncData, or similar composables
3. Client-side navigation: A user must navigate to the prerendered page (not during initial SSR hydration)

Attack Scenario

// Malicious API response during prerendering
{
  "__nuxt_island": {
    "key": "../../../../internal/service",
    "params": { "action": "probe" }
  }
}

This could cause the client to make requests to /__nuxt_island/../../../../internal/service.json if path traversal is not properly handled by the server.

Impact Assessment

• Limited Impact: The vulnerability has a low severity due to the highly specific prerequisites
• No Direct Data Exfiltration: The vulnerability does not directly expose sensitive data
• Client-Side Only: Requests originate from the client, not the server

Mitigation

Action Required:

• Update to Nuxt 3.19.0+ or 4.1.0+ immediately
• Review any prerendered pages that fetch external or user-controlled data

Temporary Workarounds (if immediate update is not possible):

1. Disable prerendering for pages that fetch user-controlled data
2. Implement strict input validation on API endpoints used during prerendering
3. Use allowlists for API response structures during prerendering

Fix Details

The fix implemented validation for Island keys in revive-payload.server.ts:

• Island keys must match the pattern /^[a-z][a-z\d-]*_[a-z\d]+$/i
• Maximum length of 100 characters
• Prevents path traversal and special characters

Summary

esbuild allows any websites to send any request to the development server and read the response due to default CORS settings.

Details

esbuild sets Access-Control-Allow-Origin: * header to all requests, including the SSE connection, which allows any websites to send any request to the development server and read the response.

https://github.com/evanw/esbuild/blob/df815ac27b84f8b34374c9182a93c94718f8a630/pkg/api/serve_other.go#L121 https://github.com/evanw/esbuild/blob/df815ac27b84f8b34374c9182a93c94718f8a630/pkg/api/serve_other.go#L363

Attack scenario:

1. The attacker serves a malicious web page (http://malicious.example.com).
2. The user accesses the malicious web page.
3. The attacker sends a fetch('http://127.0.0.1:8000/main.js') request by JS in that malicious web page. This request is normally blocked by same-origin policy, but that's not the case for the reasons above.
4. The attacker gets the content of http://127.0.0.1:8000/main.js.

In this scenario, I assumed that the attacker knows the URL of the bundle output file name. But the attacker can also get that information by

• Fetching /index.html: normally you have a script tag here
• Fetching /assets: it's common to have a assets directory when you have JS files and CSS files in a different directory and the directory listing feature tells the attacker the list of files
• Connecting /esbuild SSE endpoint: the SSE endpoint sends the URL path of the changed files when the file is changed (new EventSource('/esbuild').addEventListener('change', e => console.log(e.type, e.data)))
• Fetching URLs in the known file: once the attacker knows one file, the attacker can know the URLs imported from that file

The scenario above fetches the compiled content, but if the victim has the source map option enabled, the attacker can also get the non-compiled content by fetching the source map file.

PoC

1. Download reproduction.zip
2. Extract it and move to that directory
3. Run npm i
4. Run npm run watch
5. Run fetch('http://127.0.0.1:8000/app.js').then(r => r.text()).then(content => console.log(content)) in a different website's dev tools.

Impact

Users using the serve feature may get the source code stolen by malicious websites.

Summary

Nuxt allows any websites to send any requests to the development server and read the response due to default CORS settings.

Details

While Vite patched the default CORS settings to fix https://github.com/vitejs/vite/security/advisories/GHSA-vg6x-rcgg-rjx6, nuxt uses its own CORS handler by default (https://github.com/nuxt/nuxt/pull/23995).

https://github.com/nuxt/nuxt/blob/7d345c71462d90187fd09c96c7692f306c90def5/packages/vite/src/client.ts#L257-L263

That CORS handler sets Access-Control-Allow-Origin: *.

[!IMPORTANT]
If on an affected version, it may be possible to opt-out of the default Nuxt CORS handler by configuring vite.server.cors.

PoC

1. Start a dev server in any nuxt project using Vite by nuxt dev.
2. Send a fetch request to http://localhost:3000/_nuxt/app.vue (fetch('http://localhost:3000/_nuxt/app.vue')) from a different origin page.

Impact

Users with the default server.cors option using Vite builder may get the source code stolen by malicious websites

Additional Information

/__nuxt_vite_node__/manifest / /__nuxt_vite_node__/module also seems to have Access-Control-Allow-Origin: *, so it maybe also possible to exploit that handler. https://github.com/nuxt/nuxt/blob/7d345c71462d90187fd09c96c7692f306c90def5/packages/vite/src/vite-node.ts#L39 Although I didn't find a valid module id. Note that this handler is probably also vulnerable to DNS rebinding attacks as I didn't find any host header checks.