The undici WebSocket client, when using HTTP/2 (enabled by default with allowH2: true), crashes the Node.js process if it connects to a malicious server that responds with a failed WebSocket handshake over HTTP/2. This occurs because the client aborts the request too late, leaving an open HTTP/2 stream that emits an unhandled error when the server closes the connection, causing a denial of service. Versions 8.11.0 and 8.11.1 are affected. A fix is available in version 8.11.2. Workarounds include disabling HTTP/2 for WebSocket connections or avoiding untrusted servers until patched.