In this post, we will delve into a vulnerability in the Android operating system, identified as CVE-2017-13322. This vulnerability presents a potential risk of preventing access to emergency services due to a logic error in the PhoneInterfaceManager.java code. The implications for this could result in a local denial of service attack, with no additional execution privileges necessary for exploitation. It is important to note that user interaction is not required for this vulnerability to be exploited.

Code Snippet

The problematic code can be found in the endCallForSubscriber method of the PhoneInterfaceManager.java file. The following snippet provides an overview of the method in question:

public boolean endCallForSubscriber(long subId) {
    enforceModifyPermission();
    final long identity = Binder.clearCallingIdentity();
    try {
        // FIXME: use caller's subId
        return getPhone(subId).endCall();
    } catch (Exception e) {
        Log.w(TAG, "Error calling ITelephony#endCallForSubscriber", e);
    } finally {
        Binder.restoreCallingIdentity(identity);
    }
    return false;
}

As evident from the code snippet above, the endCallForSubscriber method contains a logic error that can potentially lead to the denial of service in emergency situations.

Exploit Details

The vulnerability lies in the enforceModifyPermission() function call. In certain scenarios, an attacker can create a situation where the emergency call does not end, thereby preventing access to emergency services since the call cannot be terminated. This blockade can further result in a local denial of service as the phone effectively becomes unusable for other purposes due to the perpetual occupying of the line.

This situation can be exploited without any user interaction and does not require additional execution privileges, making it particularly concerning for devices potentially affected by this vulnerability.

Original References

1. Android Open Source Project (AOSP): The issue was first documented in the Android Open Source Project (AOSP) and has been fixed in later versions of the Android operating system. For more details, please refer to the AOSP commit message found at https://android.googlesource.com/platform/packages/services/Telephony/+/1ef4883%5E%21/
2. CVE Details: Further information regarding this vulnerability, including score, impact, and affected software and hardware, can be found at https://www.cvedetails.com/cve/CVE-2017-13322/

Mitigation and Conclusion

It is highly recommended for users operating on vulnerable Android versions to update their software as soon as possible. Applying security patches and keeping the software updated can go a long way in preventing potential exploitation of this vulnerability.

In conclusion, the CVE-2017-13322 vulnerability in the Android operating system can potentially put users at risk by preventing access to emergency services due to a logic error in the PhoneInterfaceManager.java code. Staying vigilant and keeping software updated are crucial steps in ensuring a device's security as attackers are always on the lookout for vulnerabilities to exploit.

Timeline

Published on: 01/17/2025 23:15:10 UTC
Last modified on: 01/23/2025 19:54:01 UTC