CVE-2026-9595
5.3 · MEDIUMOverview
CVE-2026-9595 is a medium-severity vulnerability affecting webpack.js webpack-dev-server. It was published on June 15, 2026 and has a CVSS 3.1 base score of 5.3 (MEDIUM).
This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical 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 [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.
Remediation
Check the references section for vendor advisories and patches from webpack.js. Update webpack-dev-server to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| webpack.js | webpack-dev-server | >= 0, < 5.2.5 | Affected |
References
Frequently Asked Questions
What is CVE-2026-9595?
CVE-2026-9595 is a medium-severity vulnerability affecting webpack.js webpack-dev-server. It was published on June 15, 2026 and has a CVSS 3.1 base score of 5.3 (MEDIUM).
How severe is CVE-2026-9595?
This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2026-9595?
Check the references section for vendor advisories and patches from webpack.js. Update webpack-dev-server to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-9595?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-9595 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
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Browser-based exploitation validates findings with real proof-of-concept.
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