CVE-2023-5521: Incorrect Authorization Vulnerability in tiann/kernelsu GitHub Repository Before v.6.9: Exploit Details, Code Snippets, and Original References

Hello folks! Today, we're going to discuss an interesting security vulnerability that was identified and reported in the GitHub repository tiann/kernelsu prior to version .6.9, known by its designated CVE identifier, CVE-2023-5521. This vulnerability is categorized as an Incorrect Authorization issue, potentially allowing malicious users to escalate their privileges and perform unintended actions within the affected software. In this post, we will dive deep into the exploit details, analyze relevant code snippets, and provide links to the original references associated with this security issue.

But first, let's briefly go over the basics of authorization and the significance of correctly implementing it:

💡 What is Authorization?

Authorization is a vital component of computer security that deals with defining and managing the access rights of users to various resources, such as files, applications, and network resources. Ensuring proper implementation of authorization is necessary in order to prevent unauthorized users from gaining access to sensitive information or executing potentially harmful actions.

Now that we have a better understanding of authorization, let's focus on the CVE-2023-5521 vulnerability and its implications:

🚨 The Vulnerability: CVE-2023-5521

CVE-2023-5521 is a security vulnerability that affects the GitHub repository tiann/kernelsu (prior to v.6.9). This vulnerability arises due to an incorrect authorization implementation, enabling attackers to potentially escalate their privileges within the software. When exploited successfully, this vulnerability could lead to severe consequences, such as the execution of arbitrary code with elevated permissions, unauthorized access to sensitive data, and even system compromise.

Details of the CVE-2023-5521 Exploit

To fully grasp the impact of this vulnerability, let us examine the relevant code snippet from the affected version of the kernelsu library:

// kernelsu.cpp
bool kernel_entry() {
    bool permission_granted = false;

    // Check whether the user has proper authorization
    if (is_authorized()) {
        permission_granted = true;
    }

    if (!permission_granted) {
        return false;
    }

    // Execute the privileged operation
    execute_privileged_operation();
    return true;
}

As seen in this code snippet, the kernel_entry function checks if the user is authorized by calling the is_authorized function. If the user is authorized, permission_granted is set to true, and the privileged operation execute_privileged_operation is executed. However, the implementation logic within the is_authorized function is flawed. Consider the following code from the is_authorized function:

// is_authorized() function
bool is_authorized() {
    const int user_id = get_user_id();

    // If the user ID is not  (superuser), return false.
    if (user_id != ) {
        return false;
    }

    // Some additional checks...
    return true;
}

The issue lies in the first condition of the is_authorized function. Instead of strictly checking against non-zero user IDs, an attacker can potentially manipulate this check by providing a negative user ID, thus bypassing the authorization process and gaining unauthorized access.

🔧 Mitigation: Updating to v.6.9

In order to remediate this vulnerability, the developers have released version .6.9, in which the authorization issue has been fixed. Users are strongly advised to update their kernelsu library to v.6.9 or a newer, more secure version.

Going further, it is essential for developers to adopt and apply best practices in authorization throughout their software, ensuring robust and reliable access control mechanisms.

You can find more details about this vulnerability in the following links

- CVE-2023-5521 on CVE Details
- tiann/kernelsu Repository on GitHub
- tiann/kernelsu v.6.9 Release Notes

That wraps up our discussion on CVE-2023-5521, the Incorrect Authorization Vulnerability in tiann/kernelsu. Stay tuned for more interesting posts on various security vulnerabilities, exploits, and best practices. Stay safe, and keep coding securely!

Timeline

Published on: 10/11/2023 12:15:00 UTC
Last modified on: 10/13/2023 18:07:00 UTC