Vite XSS vulnerability in `server.transformIndexHtml` via URL payload
GHSA-92r3-m2mg-pj97 · CVE-2023-49293
Published · Modified
Description
Summary
When Vite's HTML transformation is invoked manually via server.transformIndexHtml, the original request URL is passed in unmodified, and the html being transformed contains inline module scripts (<script type="module">...</script>), it is possible to inject arbitrary HTML into the transformed output by supplying a malicious URL query string to server.transformIndexHtml.
Impact
Only apps using appType: 'custom' and using the default Vite HTML middleware are affected. The HTML entry must also contain an inline script. The attack requires a user to click on a malicious URL while running the dev server. Restricted files aren't exposed to the attacker.
Patches
Fixed in vite@5.0.5, vite@4.5.1, vite@4.4.12
Details
Suppose index.html contains an inline module script:
<script type="module">
// Inline script
</script>
This script is transformed into a proxy script like
<script type="module" src="/index.html?html-proxy&index=0.js"></script>
due to Vite's HTML plugin:
When appType: 'spa' | 'mpa', Vite serves HTML itself, and htmlFallbackMiddleware rewrites req.url to the canonical path of index.html,
so the url passed to server.transformIndexHtml is /index.html.
However, if appType: 'custom', HTML is served manually, and if server.transformIndexHtml is called with the unmodified request URL (as the SSR docs suggest), then the path of the transformed html-proxy script varies with the request URL. For example, a request with path / produces
<script type="module" src="/@id/__x00__/index.html?html-proxy&index=0.js"></script>
It is possible to abuse this behavior by crafting a request URL to contain a malicious payload like
"></script><script>alert('boom')</script>
so a request to http://localhost:5173/?%22%3E%3C/script%3E%3Cscript%3Ealert(%27boom%27)%3C/script%3E produces HTML output like
<script type="module" src="/@id/__x00__/?"></script><script>alert("boom")</script>?html-proxy&index=0.js"></script>
which demonstrates XSS.
PoC
- Example 1. Serving HTML from
vite devmiddleware withappType: 'custom'- Go to https://stackblitz.com/edit/vitejs-vite-9xhma4?file=main.js&terminal=dev-html
- "Open in New Tab"
- Edit URL to set query string to
?%22%3E%3C/script%3E%3Cscript%3Ealert(%27boom%27)%3C/script%3Eand navigate - Witness XSS:
- Example 2. Serving HTML from SSR-style Express server (Vite dev server runs in middleware mode):
- Go to https://stackblitz.com/edit/vitejs-vite-9xhma4?file=main.js&terminal=server
- (Same steps as above)
- Example 3. Plain
vite dev(this shows that vanillavite devis not vulnerable, providedhtmlFallbackMiddlewareis used)- Go to https://stackblitz.com/edit/vitejs-vite-9xhma4?file=main.js&terminal=dev
- (Same steps as above)
- You should not see the alert box in this case
Detailed Impact
This will probably predominantly affect development-mode SSR, where vite.transformHtml is called using the original req.url, per the docs:
However, since this vulnerability affects server.transformIndexHtml, the scope of impact may be higher to also include other ad-hoc calls to server.transformIndexHtml from outside of Vite's own codebase.
My best guess at bisecting which versions are vulnerable involves the following test script
import fs from 'node:fs/promises';
import * as vite from 'vite';
const html = `
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
</head>
<body>
<script type="module">
// Inline script
</script>
</body>
</html>
`;
const server = await vite.createServer({ appType: 'custom' });
const transformed = await server.transformIndexHtml('/?%22%3E%3C/script%3E%3Cscript%3Ealert(%27boom%27)%3C/script%3E', html);
console.log(transformed);
await server.close();
and using it I was able to narrow down to #13581. If this is correct, then vulnerable Vite versions are 4.4.0-beta.2 and higher (which includes 4.4.0).
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