With all the advances and security enhancements in technology, vulnerabilities can often lie hidden and undetected. These vulnerabilities may lead to unauthorized access or control over certain features or systems. CVE-2023-30682 is one such vulnerability that affects the Telecom systems prior to SMR (Security Maintenance Release) Aug-2023 Release 1.

In this post, we will dig deep into the details of this vulnerability, discuss the exploit, and provide insights into the related code snippet and original references. Before diving into the details, it is important to understand what improper access control means and how attackers can exploit it.

Improper Access Control

Improper access control, also known as a permission or privilege escalation vulnerability, occurs when an application or system grants unauthorized access to an attacker. Access control is crucial in ensuring that only authorized users can access specific resources or perform certain actions. When improperly implemented, attackers can exploit these vulnerabilities to gain unauthorized control or access to sensitive information, which could lead to breaches or other potential damages.

CVE-2023-30682 Overview

CVE-2023-30682 is a vulnerability in Telecom systems, specifically in versions prior to SMR Aug-2023 Release 1. It allows local attackers to call the silenceRinger API without having the proper permissions. This improper access control vulnerability can allow an attacker to silence incoming calls without the knowledge or consent of the device owner.

The silenceRinger API is designed to silence the ringer for incoming calls and is typically meant to be called only by apps with the appropriate permissions. However, a flaw in the access control implementation allows an attacker to call this API without requiring those necessary permissions.

The following code snippet demonstrates the improper permission check in the Telecom system

public class TelecomServiceImpl extends ITelecomService.Stub {

    // ...

    @Override
    public void silenceRinger() {
        enforceModifyPhoneState("silenceRinger");

        // ...

    }

    // ...

    private void enforceModifyPhoneState(String message) {
        if (getPackageManager().checkPermission(Manifest.permission.MODIFY_PHONE_STATE,
                mContext.getPackageName()) != PackageManager.PERMISSION_GRANTED) {
            throw new SecurityException(message + ": Neither user nor current process has android.permission.MODIFY_PHONE_STATE");
        }
    }

}

In the above code, the enforceModifyPhoneState() method checks whether the caller has the MODIFY_PHONE_STATE permission but fails to properly enforce it. As a result, unauthorized callers can use the silenceRinger() API.

Exploit Details

An attacker can exploit this vulnerability by crafting and installing a malicious app on the victim's device. The malicious app does not need to request the MODIFY_PHONE_STATE permission, as the improper access control flaw enables it to bypass this permission requirement.

Once installed, the app can invoke the silenceRinger() method to silence incoming calls without notifying the victim. This could allow the attacker to interfere in the device's basic functionality and communication capabilities, potentially causing further harm or enabling other attack avenues.

For further information regarding CVE-2023-30682, please refer to the following original sources

- CVE Entry - CVE-2023-30682
- National Vulnerability Database (NVD) - CVE-2023-30682

Conclusion

CVE-2023-30682 is a serious vulnerability that exists in Telecom systems prior to SMR Aug-2023 Release 1. This improper access control flaw allows an attacker to call the silenceRinger API without permission, potentially silencing incoming calls and disrupting the device's functionality. Developers should take note of this vulnerability and prioritize updating their systems to the latest SMR Aug-2023 Release 1 to mitigate the risk. Additionally, maintaining proper access control and privilege management should be a top priority in all application and system development in order to prevent unauthorized access or manipulation.

Timeline

Published on: 08/10/2023 02:15:00 UTC
Last modified on: 08/14/2023 16:15:00 UTC