CVE-2026-6402

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.

PUBLISHED Reserved 2026-04-15 | Published 2026-05-12 | Updated 2026-05-12 | Assigner openjs

Problem types

CWE-749: Exposed Dangerous Method or Function

Product status

Credits

sapphi-red reporter

Ulises Gascón remediation developer

Sebastian Beltran remediation developer

Alexander Akait remediation reviewer

References

github.com/...server/security/advisories/GHSA-79cf-xcqc-c78w

cna.openjsf.org/security-advisories.html

cve.org (CVE-2026-6402)

nvd.nist.gov (CVE-2026-6402)

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