CVE-2026-9595 webpack-dev-server vulnerable to HMR WebSocket interception via permissive user proxies

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...

CVE-2026-9595

The CVE affects webpack-dev-server where a user-configured proxy with a broad context (e.g., /) and ws: true intercepts the dev server’s HMR WebSocket, forwarding it to the proxy target. This can leak cookies and Origin headers to the backend, bypass Host/Origin validation, and corrupt the HMR so...

CVE-2026-27977

CVE-2026-27977 affects the Next.js development server. The vulnerability lies in the Next.js dev mode where cross-site protection for internal HMR websocket endpoints could treat Origin: null as a permitted bypass even when allowedDevOrigins is configured, allowing privacy-sensitive contexts (e.g...

CVE-2026-27977 Next.js: null origin can bypass dev HMR websocket CSRF checks

Next.js is a React framework for building full-stack web applications. Starting in version 16.0.1 and prior to version 16.1.7, in next dev, cross-site protection for internal websocket endpoints could treat Origin: null as a bypass case even if allowedDevOrigins is configured, allowing...

CVE-2026-27977 Next.js: null origin can bypass dev HMR websocket CSRF checks

Next.js is a React framework for building full-stack web applications. Starting in version 16.0.1 and prior to version 16.1.7, in next dev, cross-site protection for internal websocket endpoints could treat Origin: null as a bypass case even if allowedDevOrigins is configured, allowing...