CVE-2023-49293 — vite
MEDIUMCVE-2023-49293 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in vite. 1 public exploit reference exists, so weaponization risk is real. A fix is available for vite — see the affected versions and patch details below.
Cross-site Scripting in `server.transformIndexHtml` via URL payload in vite
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-49293.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2023-49293 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
vitenpmDescription
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 [email protected], [email protected], [email protected]
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).
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | vite | ≥ 4.4.0&&< 4.4.12 | 4.4.12npm install vite@4.4.12 |
| 📦npm | vite | ≥ 4.5.0&&< 4.5.1 | 4.5.1npm install vite@4.5.1 |
| 📦npm | vite | ≥ 5.0.0&&< 5.0.5 | 5.0.5npm install vite@5.0.5 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for vite, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update vite to 4.4.12 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-49293 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2023-49293 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2023-49293. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
How to detect CVE-2023-49293
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2023-49293 -u https://target- Template
- Vite dev server - Cross-Site Scripting
- Severity
- medium
- Impact
- Attackers can inject malicious HTML into the page, potentially leading to cross-site scripting or other client-side attacks.
- Remediation
- Update to [email protected], [email protected], or [email protected].
Template by ProjectDiscovery nuclei-templates (ritikchaddha), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2023-49293 in your dependencies?
O3 Security finds CVE-2023-49293 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.