CVE-2026-9595
MEDIUM EPSS 5.9%
Published Jun 15, 20262w ago · Modified Jun 17, 20262w ago
4.3 CVSS 3.1
Published Jun 15, 2026 2w ago
Last Modified Jun 17, 2026 2w ago
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.
CVSS Details
Base Score
Exploitability
Impact
Vector string
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L Attack Vector Network
Attack Complexity Low
Privileges Required Low
User Interaction None
Scope Unchanged
Confidentiality None
Integrity None
Availability Low
Threat Intelligence
EPSS Exploit Probability
5.9% percentile
Exploit & Patch Status
No Known Exploit
Patch Available
Weaknesses 2
CWE-346
CWE-441
Affected Products 1
| Vendor | Product | Version | Range |
|---|---|---|---|
| webpack.js | webpack-dev-server | * | <5.2.5 |
References 5
- cna.openjsf.org https://cna.openjsf.org/security-advisories.html
- github.com https://github.com/facebook/create-react-app/pull/7444
- github.com https://github.com/vuejs/vue-cli/commit/72ba7505aff2a8314e82aa5082379a77504a1fcb
- github.com https://github.com/webpack/webpack-dev-server/pull/4316
- github.com https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-mx8g-39q3-5c79
Remediation
- github.com https://github.com/facebook/create-react-app/pull/7444
- github.com https://github.com/vuejs/vue-cli/commit/72ba7505aff2a8314e82aa5082379a77504a1fcb
- github.com https://github.com/webpack/webpack-dev-server/pull/4316