CVE-2022-20489: Escalation of Privilege Due to Resource Exhaustion in AutomaticZenRule.java Functions

In today's post, we're going to discuss a security vulnerability with the ID CVE-2022-20489 that affects multiple Android versions, specifically Android 10, 11, 12, 12L, and 13. This vulnerability lies in a file called AutomaticZenRule.java, where a possible failure to persist permissions settings can occur due to resource exhaustion, leading to local escalation of privilege. The most concerning part is that user interaction is not required for this exploitation.

For a little more background, the AutomaticZenRule.java file is responsible for managing automatic Zen mode (also known as Do Not Disturb mode) rules in Android. When these rules aren't properly persisted due to resource exhaustion, it creates an opportunity for an attacker to take advantage of the situation and escalate their privilege level on the device without requiring any additional execution privileges or user interaction. The Android ID for this issue is A-242703460.

Let's look at a code snippet from AutomaticZenRule.java, where this vulnerability lies

public class AutomaticZenRule {
    ...
    private void updateAutomaticZenRule(AutomaticZenRule rule) {
        ...
        try {
            ...
            applyAutomaticZenRule(rule);
        } catch (Exception e) {
            Log.e(TAG, "Failed to apply AutomaticZenRule " + rule, e);
        }
    }
    ...
    private void applyAutomaticZenRule(AutomaticZenRule rule) throws Exception {
        ...
        if (rule.isEnabled() && !permissionsAreGranted(rule)) {
            // Resource exhaustion can occur here, leading to a failure to persist the proper permissions
            requestRequiredPermissions(rule);
        }
    }
}

As you can see, the applyAutomaticZenRule() function is called within a try-catch block inside the updateAutomaticZenRule() function. Here's where the problem lies: if resource exhaustion occurs during the execution of applyAutomaticZenRule(), it may fail to persist the proper permissions setting, thereby creating an opportunity for a malicious actor to exploit the situation.

Exploit Details

An attacker can exploit this vulnerability by inducing a state of resource exhaustion on a target device running one of the affected Android versions (10, 11, 12, 12L, or 13). This can be achieved through various methods, such as generating a large number of separate automatic Zen rules or by causing the device to run low on system resources in general.

Once the device is in a state of resource exhaustion, if the user tries to update or create a new automatic Zen rule, it can trigger the vulnerability in the applyAutomaticZenRule() function. This can lead to permissions not being properly persisted, giving the attacker an opportunity to escalate their privileges on the device without the need for any additional execution privileges or user interaction.

Here are some links to the original references for this vulnerability

1. The official CVE page for CVE-2022-20489: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-20489.
2. The Android Security Bulletin, where this vulnerability is listed: https://source.android.com/security/bulletin/.

Mitigation

To mitigate this vulnerability, it's essential to keep your Android device up to date with the latest security patches. Android periodically releases security updates that address known issues such as this one. As a user, always ensure you're using the latest available version of Android for your device and pay attention to any new security updates.

Conclusion

The CVE-2022-20489 vulnerability demonstrates how a seemingly small issue in an Android system file like AutomaticZenRule.java can lead to potentially severe consequences, such as local privilege escalation. As a user, always be vigilant with your device's security practices, like keeping your device updated and being cautious of suspicious apps and activities.

Timeline

Published on: 01/26/2023 21:15:00 UTC
Last modified on: 02/01/2023 15:38:00 UTC