CVE-2026-9595 (GCVE-0-2026-9595)

Vulnerability from cvelistv5 – Published: 2026-06-15 15:00 – Updated: 2026-06-15 16:08
VLAI
Title
webpack-dev-server vulnerable to HMR WebSocket interception via permissive user proxies
Summary
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.
Severity
5.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-15 16:08 UTC
CWE
  • CWE-346 - Origin Validation Error
  • CWE-441 - Unintended Proxy or Intermediary ('Confused Deputy')
Assigner
References
Impacted products
Vendor Product Version CPE status
webpack-dev-server webpack-dev-server Affected: 0 , < 5.2.5 (semver)
Unaffected: 5.2.5 (semver)
guessed Create a notification for this product.
Credits
bjohansebas UlisesGascon ajhyndman
Show details on NVD website
To clipboard 

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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