CVE-2026-9595

Name: CVE-2026-9595
Creator: NVD / NIST
Published: 2026-06-15T16:16:35.227+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.3/10EPSS 0.16%

Last modified Jun 17, 2026

CVE-2026-9595 is a medium-severity vulnerability rated 4.3/10 on the CVSS scale. 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. EPSS estimates a 0.16% chance of exploitation in the next 30 days.

Description

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 header to the backend, bypasses the dev server's Host/Origin validation, and corrupts the HMR socket (both HMR and the proxy end up writing to the same socket). Patches: Fixed in webpack-dev-server@5.2.5. Workarounds: Scope user-defined proxy context to specific paths instead of /, or omit ws: true from the proxy entry when WebSocket forwarding is not required.

Metrics

CVSS 3.1

4.3/10

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

EPSS Probability

0.16%

5.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Webpack.Js	Webpack-Dev-Server	< 5.2.5

References

https://cna.openjsf.org/security-advisories.htmlVendor Advisory
https://github.com/facebook/create-react-app/pull/7444Issue Tracking, Patch
https://github.com/vuejs/vue-cli/commit/72ba7505aff2a8314e82aa5082379a77504a1fcbPatch
https://github.com/webpack/webpack-dev-server/pull/4316Issue Tracking, Patch
https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-mx8g-39q3-5c79Mitigation, Vendor Advisory

Timeline

Published: Jun 15, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-9595?

How severe is CVE-2026-9595?

CVE-2026-9595 has a CVSS score of 4.3/10 (MEDIUM severity). The EPSS model estimates a 0.16% probability of exploitation in the next 30 days.

How do I fix CVE-2026-9595?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-9595?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST