Vulnerability · Published May 12, 2026 · Assigned by openjs
CVE-2026-6402webpack-dev-server vulnerable to cross-origin source code exposure on non-HTTPS origins
Medium 5.3
In plain English
A medium-severity security flaw in webpack-dev-server from webpack-dev-server. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 22% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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 & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| npm | webpack-dev-server | 5.2.4 | GHSA-79cf-xcqc-c78w |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| webpack-dev-server | webpack-dev-server | 0 – before 5.2.4 |
Weakness: CWE-749 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N