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
Affected Vendors & Products
References
History
Tue, 16 Jun 2026 17:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| CPEs | cpe:2.3:a:webpack.js:webpack-dev-server:*:*:*:*:*:*:*:* |
Tue, 16 Jun 2026 14:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Webpack.js
Webpack.js webpack-dev-server |
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| Vendors & Products |
Webpack.js
Webpack.js webpack-dev-server |
Mon, 15 Jun 2026 18:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Metrics |
ssvc
|
Mon, 15 Jun 2026 16:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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. | |
| Title | webpack-dev-server vulnerable to HMR WebSocket interception via permissive user proxies | |
| Weaknesses | CWE-346 CWE-441 |
|
| References |
|
|
| Metrics |
cvssV3_1
|
Status: PUBLISHED
Assigner: openjs
Published: 2026-06-15T15:00:21.488Z
Updated: 2026-06-15T16:08:35.549Z
Reserved: 2026-05-26T14:38:47.772Z
Link: CVE-2026-9595
Updated: 2026-06-15T16:08:30.548Z
Status : Analyzed
Published: 2026-06-15T16:16:35.227
Modified: 2026-06-16T17:24:37.060
Link: CVE-2026-9595
No data.