What is CVE-2026-9595?

CVE-2026-9595 is a medium-severity vulnerability in Webpack-dev-server, classified under Origin Validation Error. CVSS score: 5.3/10. Published 2026-06-15.

How severe is CVE-2026-9595?

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

Vulnerability in Webpack-dev-server

CVE-2026-9595

Impact: When a user-configured proxy on webpack-dev-server has a broad context (e.g. /) and ws: true, it also intercepts the dev server's own HMR WebSocket and forwards it to the proxy target. This leaks the browser's cookies and Origin he…

CVSS v3 metric

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

Affected products

Webpack-dev-server — versions 0, 5.2.5
Webpack.js Webpack-dev-server

Weakness classification (CWE)

References

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

Frequently asked questions

What is CVE-2026-9595?: CVE-2026-9595 is a medium-severity vulnerability in Webpack-dev-server, classified under Origin Validation Error. CVSS score: 5.3/10. Published 2026-06-15.
How severe is CVE-2026-9595?: Medium severity. CVSS v3 base score is 5.3 out of 10.