What is CVE-2026-6402?

CVE-2026-6402 is a medium-severity vulnerability in Webpack-dev-server, classified under CWE-749. CVSS score: 5.3/10. Published 2026-05-12.

How severe is CVE-2026-6402?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Vulnerability in Webpack-dev-server

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 origin such as plain HTTP. The previous fix relied on the Sec-Fetch-Mode and Sec-Fetc…

EPSS: 0.000 (9.9th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N.

Affected products

Webpack-dev-server — versions 0, 5.2.4
Webpack.js Webpack-dev-server

Weakness classification (CWE)

CWE-749

References

ce714d77-add3-4f53-aff5-83d477b104bb (Mitigation, Vendor Advisory)
ce714d77-add3-4f53-aff5-83d477b104bb (Vendor Advisory)

Frequently asked questions

What is CVE-2026-6402?: CVE-2026-6402 is a medium-severity vulnerability in Webpack-dev-server, classified under CWE-749. CVSS score: 5.3/10. Published 2026-05-12.
How severe is CVE-2026-6402?: Medium severity. CVSS v3 base score is 5.3 out of 10.