CVE-2024-26465: Exploring the DOM-based XSS Vulnerability in Stewdio Beep.js and Mitigating the Risk

The CVE-2024-26465 vulnerability refers to a DOM-based cross-site scripting (XSS) issue found in the component /beep/Beep.Instrument.js of stewdio beep.js before commit ef22ad7. This vulnerability allows attackers to execute arbitrary JavaScript code by sending a crafted URL to the victim. In this post, we will delve into the details of this vulnerability, discussing the exploit and potential ways to mitigate the risk.

Exploit Details

A DOM-based XSS vulnerability occurs when a web application inserts untrusted data into the Document Object Model (DOM) of a webpage without proper sanitization or output encoding. The security flaw lies in the /beep/Beep.Instrument.js file of beep.js, which does not adequately validate user input before rendering it as part of the DOM. As a result, an attacker can exploit this weakness by crafting a malicious URL containing the XSS payload and tricking the victim into clicking it.

Here's a code snippet from the vulnerable version of /beep/Beep.Instrument.js that contains the DOM-based XSS vulnerability:

//beep/Beep.Instrument.js
function loadInstrument(data) {
    var instrumentData = JSON.parse(data);
    var instrumentName = instrumentData.name;
    document.getElementById('instrumentName').innerHTML = instrumentName;
}

As seen in this code snippet, the loadInstrument function takes the user-supplied data and directly assigns it to the innerHTML property of an element with the ID 'instrumentName'. This allows an attacker to inject arbitrary JavaScript code by crafting a URL with a malicious payload.

An example of a crafted URL that exploits this vulnerability

https://example.com/beep?instrument=%7B%22name%22%3A%22%3Cscript%3Ealert%28%27XSS%27%29%3B%3C%2Fscript%3E%22%7D

When a victim clicks on this URL, the alert('XSS') script will execute, confirming the presence of DOM-based XSS vulnerability.

Mitigation

To remediate this vulnerability, developers should sanitize user input and use proper output encoding when rendering user data in the DOM. One possible approach is to use the widely supported .textContent property instead of .innerHTML when assigning user-supplied data to a DOM element.

Here's an updated version of the vulnerable code snippet in /beep/Beep.Instrument.js that mitigates the DOM-based XSS vulnerability:

//beep/Beep.Instrument.js
function loadInstrument(data) {
    var instrumentData = JSON.parse(data);
    var instrumentName = instrumentData.name;
    document.getElementById('instrumentName').textContent = instrumentName;
}

By assigning the user-supplied data to the textContent property instead of innerHTML, the data is treated as plain text, not HTML or JavaScript, preventing the execution of any arbitrary script.

Conclusion

Understanding and mitigating the CVE-2024-26465 DOM-based XSS vulnerability in Stewdio Beep.js is essential for ensuring secure web applications. Developers should always strive to sanitize user input and use proper output encoding while rendering data in the DOM. Furthermore, being aware of such threats is crucial for both developers and web users for a safer online experience.

For more information on this vulnerability, you can visit the following resources

1. Original Reference to Commit ef22ad7
2. DOM-based XSS Prevention Cheat Sheet
3. Stewdio Beep.js Project Repository

Timeline

Published on: 02/26/2024 16:27:59 UTC
Last modified on: 02/26/2024 16:32:25 UTC