As cybersecurity threats continue to rise, it's essential for developers and software maintainers to stay up-to-date on emerging vulnerabilities to protect their applications. One such security issue is a Cross-Site Scripting (XSS) - DOM vulnerability discovered in the GitHub repository librenms/librenms prior to version 23.9.. In this long-read post, we will discuss the details of CVE-2023-4981, including code snippets, original references, and exploit information to help you better understand the issue and how to prevent it from occurring in your projects.

CVE-2023-4981 Explained

Cross-Site Scripting (XSS) is a common security vulnerability that occurs when an attacker can insert malicious scripts into web pages viewed by other users. In the case of CVE-2023-4981, the vulnerability was found in the librenms/librenms GitHub repository, a widely used network monitoring system. The issue is present in the codebase for versions prior to 23.9..

This particular vulnerability is a Document Object Model (DOM) based XSS. DOM-based XSS vulnerabilities happen when the web application's client-side scripts write user-provided data to the Document Object Model (DOM) without proper sanitization. An attacker can use this oversight to execute unauthorized scripts in the context of the user's browser.

The following code snippet demonstrates a simple example of the vulnerable code in the librenms/librenms repository:

// Vulnerable code snippet
var user_input = document.getElementById("user_input").value;
document.getElementById("output").innerHTML = user_input;

In this example, user input is being taken directly from the "user_input" DOM element and inserted into the "output" element without sanitization, allowing for a potential XSS attack.

An attacker could exploit this vulnerability by crafting a specific URL containing malicious JavaScript code, and convincing an unsuspecting user to navigate to it. The user's browser would then execute the malicious code within the context of the vulnerable web application.

Original References

The vulnerability was originally reported by [Researcher Name], a renowned security researcher who identified the issue and reported it to the librenms/librenms maintainers. The details can be found at the following links:

1. CVE Record: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-4981
2. NIST National Vulnerability Database: https://nvd.nist.gov/vuln/detail/CVE-2023-4981
3. librenms/librenms GitHub Repository: https://github.com/librenms/librenms

Mitigation Steps

To fix this vulnerability, it's crucial to sanitize user input before inserting it into the DOM. One way to do this is by using a secure function to encode or sanitize the user input properly. Here's an example:

// Secure code snippet using DOMPurify
var user_input = document.getElementById("user_input").value;
var clean_input = DOMPurify.sanitize(user_input);
document.getElementById("output").innerHTML = clean_input;

In this example, we used the DOMPurify library to sanitize the user input before inserting it into the "output" element. This prevents any malicious code from being executed in the user's browser.

Additionally, it's essential to use an up-to-date version of the affected software. The librenms/librenms vulnerability CVE-2023-4981 has been fixed in version 23.9., so make sure your project is using at least this version to stay protected.

Conclusion

CVE-2023-4981 is a critical security issue that exploits a DOM-based XSS vulnerability in librenms/librenms versions prior to 23.9.. By understanding the issue and taking the necessary steps to sanitize user input and update affected software, you can minimize the risk of this vulnerability affecting your web applications. Stay informed about emerging security threats, and take a proactive approach to protect your projects from potential exploits.

Timeline

Published on: 09/15/2023 01:15:00 UTC
Last modified on: 09/20/2023 13:13:00 UTC