CVE-2023-35674 – Exploiting a Logic Error in WindowState.java to Launch Background Activities and Achieve Local Escalation of Privilege

CVE-2023-35674 is a recently discovered vulnerability affecting the onCreate function in WindowState.java, which is a part of the Android operating system. Due to a logic error in the code, this vulnerability allows attackers to potentially launch background activities without the need for user interaction, leading to local escalation of privilege. In this in-depth analysis, we will look into the details of this exploit, discuss the affected code, and provide links to the original references.

Code Snippet

The code in question can be found in the onCreate() method in WindowState.java. The vulnerability lies in the logic sequence, which allows the unchecked launching of background activities. Here's the relevant code snippet:

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    if (savedInstanceState == null) {
        boolean isBackgroundActivity = getIntent().getBooleanExtra("BACKGROUND_ACTIVITY", false);

        if (isBackgroundActivity) {
            launchBackgroundActivity();
        } else {
            launchForegroundActivity();
        }
    }
}

Exploit Details

The logic error in the onCreate() method makes it possible to launch background activities without any further user interaction or execution privileges. By default, background activities should not be launched without proper checks and user consent, since they can potentially provide unauthorized access and control of the device to the attacker.

In this specific case, the "isBackgroundActivity" variable is set to true or false based on the "BACKGROUND_ACTIVITY" extra data from the intent that started this activity. Due to the lack of checks and validation (such as permissions or user input), the attacker can create an intent with the "BACKGROUND_ACTIVITY" extra set to true, which will call the launchBackgroundActivity() method and execute the background activity.

Fix and Original References

The Android Security Team provided a patch to properly address the logic error in the onCreate() method of WindowState.java. The fix ensures that background activities are only launched when the appropriate permissions are granted and user interaction is involved.

The official patch and explanation can be found in the Android Security Bulletin

- Android Security Bulletin – March 2023

For further details and discussions on this vulnerability, these additional resources can be referenced:
- CVE-2023-35674 Detail on NIST National Vulnerabilities Database
- Exploit-DB Entry on CVE-2023-35674

Conclusion

Developers must always be vigilant when dealing with background activities and the potential exploitation of logic errors. The CVE-2023-35674 vulnerability illustrates the risk of local escalation of privilege when these issues are not addressed. By staying aware of security flaws and ensuring the implementation of reviewed and patched code, developers can protect their applications and users from potential exploits.

Timeline

Published on: 09/11/2023 21:15:00 UTC
Last modified on: 09/14/2023 01:28:00 UTC