CVE-2022-41940 is a critical vulnerability affecting the Engine.IO, which is an implementation of transport-based cross-browser/cross-device bi-directional communication layer for Socket.IO. This security issue goes as far as impacting all the users of the package, including developers who utilize its dependent packages like Unfortunately, there is no known workaround for this vulnerability, and the only surefire solution is to upgrade to a safe version.

In this article, we discuss the CVE-2022-41940 vulnerability in detail, including its exploit details, code snippets, links to original references, and the patch released to address this issue.

Exploit Details

A specially crafted HTTP request can trigger an uncaught exception on the Engine.IO server, which in turn ends up killing the Node.js process. Understandably, this poses a significant threat to system stability, security, and performance.

An attacker can craft and send malicious HTTP requests and exploit this vulnerability to cause a denial of service (DoS) attack, in which the server is overwhelmed with requests and ceases to function correctly, impacting regular users' experience.

Code Snippet

The vulnerable code is present in the websocket.js file within the package. Here's a code snippet that demonstrates the issue:

    // vulnerable code within websocket.js
    WebSocket.prototype.onerror = function (err) {
      this.readyState = WebSocket.CLOSED;
      this.emit('error', err);

As evident from the code snippet above, there is an uncaught exception event that occurs in the onerror function. When this event triggers, the process terminates, leading to a denial of service.

For more information about this vulnerability and related discussion, you can refer to the following original sources:

1. GitHub Issue:
2. CVE Details:


To address this issue, patches have been released in the Engine.IO versions 3.6.1 and 6.2.1. By upgrading to these safe versions, developers can mitigate the vulnerability and help maintain the overall security of their Node.js applications.

To upgrade the package, you can use the following commands depending on your package manager:

    # For npm users:
    npm install

    # For yarn users:
    yarn upgrade


CVE-2022-41940 is a critical vulnerability in the Engine.IO implementation, which, if exploited, can compromise the stability, security, and performance of Node.js applications. The only known solution to this issue is to upgrade to a safe version of the Engine.IO package, as mentioned above. Developers and users should implement the suggested patches to ensure their applications' safety and provide a secure environment for their users.


Published on: 11/22/2022 01:15:00 UTC
Last modified on: 11/26/2022 03:26:00 UTC