CVE-2026-9595
4.3
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Exploitability: 2.8 / Impact: 1.4
Source: NVD
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.
Affected (1)
Products: Webpack.js: Webpack Dev Server
Configuration A
| Vulnerable Software | Affected Versions |
|---|---|
| Before 5.2.5 |
Related CWEs
CWE-346
Origin Validation Error
The product does not properly verify that the source of data or communication is valid.
CWE-441
Unintended Proxy or Intermediary ('Confused Deputy')
The product receives a request, message, or directive from an upstream component, but the product does not sufficiently preserve the original source of the request before forwarding the request to an external actor that is outside of the product's control sphere. This causes the product to appear to be the source of the request, leading it to act as a proxy or other intermediary between the upstream component and the external actor.
References (5)
Source: ce714d77-add3-4f53-aff5-83d477b104bb
Vendor Advisory
Source: ce714d77-add3-4f53-aff5-83d477b104bb
Issue TrackingPatch
Source: ce714d77-add3-4f53-aff5-83d477b104bb
Patch
Source: ce714d77-add3-4f53-aff5-83d477b104bb
Issue TrackingPatch
Source: ce714d77-add3-4f53-aff5-83d477b104bb
MitigationVendor Advisory
Timeline
No history available yet.