CVE-2026-9595

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.

References

https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-mx8g-39q3-5c79

https://github.com/webpack/webpack-dev-server/pull/4316

https://github.com/vuejs/vue-cli/commit/72ba7505aff2a8314e82aa5082379a77504a1fcb

https://github.com/facebook/create-react-app/pull/7444

https://cna.openjsf.org/security-advisories.html

Details

Source: Mitre, NVD

Risk Information

CVSS v2

CVSS v3