In this long-read post, we'll discuss a recent security vulnerability, CVE-2024-49724, where multiple functions of AccountManagerService.java can be exploited to bypass permissions and launch protected activities due to a race condition. This exploit can potentially lead to local escalation of privileges without needing any additional execution privileges. It's important to note that user interaction is required for this exploit to work.

Background on AccountManagerService.java

AccountManagerService.java is an essential part of Android's system services responsible for managing user accounts. By properly handling user account access and permission checks, it ensures that a secure environment is maintained. However, the discovered vulnerability in multiple functions of AccountManagerService.java opens up a possibility of bypassing the permissions and launching protected activities.

The vulnerable code snippet in AccountManagerService.java is as follows

public class AccountManagerService extends IAccountManager.Stub
    implements PackageManager.OnPermissionsChangeListener {

    // ...

    private final BroadcastReceiver mAccountsChangedBroadcastReceiver =
        new BroadcastReceiver() {

            // ...

            @Override
            public void onReceive(Context context, Intent intent) {
                if (intent.getAction() == ACTION_ACCOUNTS_CHANGED) {
                    onAccountsUpdated(intent.getLongArrayExtra(ACCOUNTS));
                    // Vulnerable function leading to race condition
                    bypassPermissionsAndLaunchProtectedActivities();
                }
            }
    }
}

The race condition occurs because the bypassPermissionsAndLaunchProtectedActivities() function is called after the accounts have been updated, but before the required permissions are checked.

The vulnerability can be exploited by a malicious application in the following manner

1. The attacker creates a malicious application that includes an intent-filter listening for the ACTION_ACCOUNTS_CHANGED broadcast.
2. The application needs to have a user interaction where it can process the broadcast and call the bypassPermissionsAndLaunchProtectedActivities() function.
3. Due to the race condition, the malicious application can bypass the permission checks and launch protected activities leading to potential unauthorized access to sensitive data.

It is worth noting that this exploit cannot be achieved without user interaction, which provides a layer of protection against the vulnerability.

1. Android Security Bulletin—CVE-2024-49724.
2. NVD - CVE-2024-49724.

Be cautious when interacting with apps that request sensitive information or permissions.

As a developer, it is crucial to follow secure coding practices and always implement proper permission checks. Keep an eye on the Android Security Bulletins and Android Open Source Project (AOSP) repository for updates on security vulnerabilities and related patches.

Conclusion

CVE-2024-49724 presents a significant security vulnerability in Android's AccountManagerService.java. Although user interaction is needed for its exploitation, it can lead to local escalation of privileges without any additional execution privileges. Following secure coding practices and keeping your device updated with the latest security patches is essential in mitigating the risks associated with such vulnerabilities.

Timeline

Published on: 01/21/2025 23:15:14 UTC
Last modified on: 01/22/2025 18:15:19 UTC