CVE-2026-6402 MEDIUM

CVE-2026-6402: webpack-dev-server vulnerable to cross-origin source code exposure on non-HTTPS origins

Vendor Webpack-Dev-Server
Product webpack-dev-server
Weakness CWE-749
Published May 12, 2026
Last update May 12, 2026

CVSS base score

5.3/10
Attack vector Network
Attack complexity High
Privileges required None
User interaction Required
Confidentiality High
Integrity None

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

May 12, 2026 CVE published
May 12, 2026 Record updated