CVE-2023-41049: Vulnerability in @dcl/single-sign-on-client Library

The popular open-source npm library, @dcl/single-sign-on-client, has recently come under the spotlight due to a new vulnerability in its code. This library is widely used for handling single sign-on authentication flows in various applications, making this security flaw a critical point of concern. This post aims to provide a comprehensive overview of the vulnerability, CVE-2023-41049, including an explanation of the issue, a code snippet illustrating the problem, links to original references, and information about the exploit and mitigation strategies.

Vulnerability Details

This vulnerability has been identified as CVE-2023-41049 and is present in versions of @dcl/single-sign-on-client before .1.. The issue resides in an improper input validation in the init function of the library. This flaw allows an attacker to execute arbitrary JavaScript code by using the javascript: prefix.

Here is a code snippet showcasing the vulnerability

// Vulnerable code in @dcl/single-sign-on-client (before version .1.)

function init(url) {
  // Improper input validation
  if (url.startsWith('javascript:')) {
    throw new Error('Invalid URL');
  }
  // ...
}

The issue stems from improper input validation that does not account for all potentially malicious inputs, such as the javascript: prefix. This oversight allows the attacker to execute the arbitrary JavaScript code.

For more information, refer to the following original references and resources

1. GitHub Issue
2. NPM Advisory
3. CVE Database Entry

Exploit

An attacker can exploit this vulnerability by providing a malicious URL with the javascript: prefix as input to the vulnerable init() function. When the application processes this input, the URL will bypass the input validation, and the arbitrary JavaScript code within the URL will be executed.

Example

// Exploit code
const maliciousURL = "javascript:alert('XSS');";
init(maliciousURL);

Mitigation

The vulnerability has been patched in the latest version of @dcl/single-sign-on-client, i.e., version .1.. It is strongly advised that users upgrade their library instances to the patched version. Updating your package.json to the following:

"@dcl/single-sign-on-client": "^.1."

For users unable to upgrade their library instances for various reasons, it is recommended that they implement additional precautions to restrict untrusted user input to the init function.

Conclusion

CVE-2023-41049 is a severe vulnerability within the @dcl/single-sign-on-client library that poses a significant risk for any application relying on this library for single sign-on authentication flows. By being aware of this vulnerability and its potential impact, developers can take steps to ensure the appropriate measures are implemented, such as upgrading to the patched version or restricting untrusted user input. By doing so, developers can protect their applications from arbitrary JavaScript execution and secure their users' data.

Timeline

Published on: 09/01/2023 20:15:07 UTC
Last modified on: 09/06/2023 00:02:42 UTC