CVE-2026-6402
webpack-dev-server versions up to and including 5.2.3 are vulnerable to cross-origin source code exposure when serving over a non-potentially trustworthy origi…
Impact
webpack-dev-server versions up to and including 5.2.3 are vulnerable to cross-origin source code exposure when serving over a non-potentially trustworthy origin such as plain HTTP. The previous fix relied on the Sec-Fetch-Mode and Sec-Fetch-Site request headers, which browsers omit for non-trustworthy origins, allowing a malicious site to load the bundled source as a script and read it across origins. Impact: an attacker controlling a website visited by a developer running webpack-dev-server can recover the application source code when the dev server runs over HTTP at a guessable host and port. Chromium based browsers from Chrome 142 onward are not affected due to local network access restrictions. Upgrade to webpack-dev-server 5.2.4 or later, which sets Cross-Origin-Resource-Policy: same-origin on responses.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | webpack-dev-server | <= 5.2.3 | 5.2.4 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Webpack.Js | Webpack-Dev-Server | before 5.2.4 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-79cf-xcqc-c78w
- https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-4v9v-hfq4-rm2v
- https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-79cf-xcqc-c78w
- https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-9jgg-88mc-972h
- https://nvd.nist.gov/vuln/detail/CVE-2026-6402
- https://cna.openjsf.org/security-advisories.html