CVE-2021-32640

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`](https://nodejs.org/api/cli.html#cli_max_http_header_size_size) and/or the [`maxHeaderSize`](https://nodejs.org/api/http.html#http_http_createserver_options_requestlistener) options.

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`](https://nodejs.org/api/cli.html#cli_max_http_header_size_size) and/or the [`maxHeaderSize`](https://nodejs.org/api/http.html#http_http_createserver_options_requestlistener) options.

### Impact A specially crafted value of the `Sec-Websocket-Protocol` header can be used to significantly slow down a ws server. ### Proof of concept ```js for (const length of [1000, 2000, 4000, 8000, 16000, 32000]) { const value = 'b' + ' '.repeat(length) + 'x'; const start = process.hrtime.bigint(); value.trim().split(/ *, */); const end = process.hrtime.bigint(); console.log('length = %d, time = %f ns', length, end - start); } ``` ### Patches The vulnerability was fixed in ws@7.4.6 (https://github.com/websockets/ws/commit/00c425ec77993773d823f018f64a5c44e17023ff) and backported to ws@6.2.2 (https://github.com/websockets/ws/commit/78c676d2a1acefbc05292e9f7ea0a9457704bf1b) and ws@5.2.3 (https://github.com/websockets/ws/commit/76d47c1479002022a3e4357b3c9f0e23a68d4cd2). ### Workarounds 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`](https://nodejs.org/api/cli.html#cli_max_http_header_size_size) and/or the [`maxHeaderSize`](https://nodejs.org/api/http.html#http_http_createserver_options_requestlistener) options. ### Credits The vulnerability was responsibly disclosed along with a fix in private by [Robert McLaughlin](https://github.com/robmcl4) from University of California, Santa Barbara.

### Impact A specially crafted value of the `Sec-Websocket-Protocol` header can be used to significantly slow down a ws server. ### Proof of concept ```js for (const length of [1000, 2000, 4000, 8000, 16000, 32000]) { const value = 'b' + ' '.repeat(length) + 'x'; const start = process.hrtime.bigint(); value.trim().split(/ *, */); const end = process.hrtime.bigint(); console.log('length = %d, time = %f ns', length, end - start); } ``` ### Patches The vulnerability was fixed in ws@7.4.6 (https://github.com/websockets/ws/commit/00c425ec77993773d823f018f64a5c44e17023ff) and backported to ws@6.2.2 (https://github.com/websockets/ws/commit/78c676d2a1acefbc05292e9f7ea0a9457704bf1b) and ws@5.2.3 (https://github.com/websockets/ws/commit/76d47c1479002022a3e4357b3c9f0e23a68d4cd2). ### Workarounds 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`](https://nodejs.org/api/cli.html#cli_max_http_header_size_size) and/or the [`maxHeaderSize`](https://nodejs.org/api/http.html#http_http_createserver_options_requestlistener) options. ### Credits The vulnerability was responsibly disclosed along with a fix in private by [Robert McLaughlin](https://github.com/robmcl4) from University of California, Santa Barbara.

ws es una biblioteca de servidor y cliente WebSocket de código abierto para Node.js. Un valor especialmente diseñado del encabezado "Sec-Websocket-Protocol" puede ser usado para ralentizar significativamente un servidor ws. La vulnerabilidad ha sido corregida en la versión ws@7.4.6 (https://github.com/websockets/ws/commit/00c425ec77993773d823f018f64a5c44e17023ff). En las versiones vulnerables de ws, el problema puede ser mitigado al reducir la longitud máxima permitida de los encabezados de petición utilizando [`--max-http-header-size=size`](https://nodejs.org/api/cli.html#cli_max_http_header_size_size) y/o las opciones [`maxHeaderSize`](https://nodejs.org/api/http.html#http_http_createserver_options_requestlistener)