Bug 2488934 (CVE-2026-9595) - CVE-2026-9595 webpack-dev-server: webpack-dev-server: Information disclosure and denial of service via improper proxy configuration
Summary: CVE-2026-9595 webpack-dev-server: webpack-dev-server: Information disclosure ...
Keywords:
Status: NEW
Alias: CVE-2026-9595
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 2489280 2489287 2489289 2489294 2489283 2489290 2489291 2489293
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-06-15 16:01 UTC by OSIDB Bzimport
Modified: 2026-08-15 08:28 UTC (History)
91 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Embargoed:

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System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2026:41951 0 None None None 2026-07-20 11:57:28 UTC

Description OSIDB Bzimport 2026-06-15 16:01:38 UTC 
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.

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.
Comment 3 errata-xmlrpc 2026-07-20 11:57:23 UTC 
This issue has been addressed in the following products:

  Red Hat Data Grid 8.6.2

Via RHSA-2026:41951 https://access.redhat.com/errata/RHSA-2026:41951
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