CVE-2026-9595

What it is

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 [email protected]. 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.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-06-15 16:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 11:05 UTC Last updatedMost recent change to the record

Details

Published

2026-06-15 16:16 UTC

Last modified

2026-06-17 11:05 UTC

Exploit probability

0.2% · EPSS, next 30 days

Weakness

CWE-346

Record status

Analyzed

Affected

• webpack.js webpack-dev-server < 5.2.5

Attack profile CVSS 3.1 · 5.3

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

Low