A critical vulnerability, identified as CVE-2022-2421, has been discovered in the popular JavaScript library Socket.IO. The vulnerability is due to improper type validation in attachment parsing, which allows an attacker to overwrite the _placeholder object, effectively placing references to functions in arbitrary positions within the resultant query object. The potential impact of this vulnerability includes the execution of arbitrary code, leading to server compromise and sensitive data exposure. In this article, we will discuss the details of CVE-2022-2421, demonstrate a code snippet containing the vulnerability, provide links to original references, and discuss possible exploit details.

Vulnerability Details

The core of the issue lies in the attachment parsing section of the Socket.IO library. When handling objects with a specific structure, the library fails to properly validate the object's type, allowing an attacker to overwrite the _placeholder object. This enables the attacker to place references to functions in arbitrary locations in the resulting query object, which may lead to unwarranted access to the server, and enable execution of arbitrary code.

Here's an example of a vulnerable code snippet

// Socket.IO attachment parsing example
function attach(data) {
  if (data && data.hasOwnProperty('_placeholder') && typeof data.num === 'number') {
    return buffers[data.num]; // potentially unsafe reference to a function
  }
  return data;
}

function parse(data) {
  if (!data || !data.hasOwnProperty('_placeholder')) {
    return data;
  }

  return attach(data); // calls the function without proper type validation
}

In the code above, the attach() function returns a potentially unsafe reference to a function due to insufficient type checking, while the parse() function calls attach() without proper type validation. The following JSON object could potentially overwrite the _placeholder object:

{
  "_placeholder": true,
  "num": "constructor.prototype.yourOwnProperty"
}

Exploit Details

An attacker can exploit CVE-2022-2421 to overwrite the _placeholder object and place references to their own malicious functions in the query object. By sending specially crafted WebSocket messages, they can trigger unwanted behavior in the Socket.IO application, potentially gaining full access to the server and causing damage or stealing data.

An example exploit may involve the following steps

1. Crafting a specially crafted WebSocket message containing the malicious JSON object that overwrites the _placeholder object.

Sending the WebSocket message to the target Socket.IO application.

3. The application processes the message while unknowingly using the malicious function references from the _placeholder object.
4. The attacker gains control over the server and executes arbitrary code, leading to potential data exposure or further compromise.

For further information on CVE-2022-2421, please refer to the following original references

- CVE-2022-2421 - Vulnerability Details
- GitHub Issue for the Socket.IO Vulnerability
- Official Socket.IO Advisory

Conclusion

CVE-2022-2421 is a critical vulnerability in the Socket.IO JavaScript library that allows an attacker to overwrite the _placeholder object due to improper type validation in attachment parsing. This enables the attacker to execute arbitrary code and potentially compromise server resources and sensitive data. Developers using Socket.IO should immediately update their library to the latest patched version to mitigate the risks associated with this vulnerability.

Timeline

Published on: 10/26/2022 10:15:00 UTC
Last modified on: 11/02/2022 19:15:00 UTC