ws is an open source WebSocket client and server library for Node.js. A specially crafted value of the Sec-Websocket-Protocol
header can be used to significantly slow down a ws server. The vulnerability has been fixed in ws@7.4.6 (https://github.com/websockets/ws/commit/00c425ec77993773d823f018f64a5c44e17023ff). In vulnerable versions of ws, the issue can be mitigated by reducing the maximum allowed length of the request headers using the --max-http-header-size=size
and/or the maxHeaderSize
options.