CVE-2022-20456: Google Android Privilege Escalation Flaw

CVE-2022-20456 Overview

CVE-2022-20456 is a local privilege escalation vulnerability affecting Google Android devices running versions 10 through 13. The vulnerability exists in the AutomaticZenRule.java component, where a resource exhaustion condition can cause a failure to persist permissions settings. This flaw allows a local attacker to escalate privileges without requiring additional execution privileges or user interaction.

Critical Impact

Local privilege escalation on Android devices through resource exhaustion, enabling attackers to bypass permission persistence mechanisms without user interaction.

Affected Products

• Google Android 10.0
• Google Android 11.0
• Google Android 12.0
• Google Android 12.1 (12L)
• Google Android 13.0

Discovery Timeline

• 2023-01-26 - CVE-2022-20456 published to NVD
• 2025-04-02 - Last updated in NVD database

Technical Details for CVE-2022-20456

Vulnerability Analysis

The vulnerability resides in the AutomaticZenRule class within AutomaticZenRule.java, a component of the Android Do Not Disturb (DND) framework. AutomaticZenRule objects define rules that automatically enable DND mode based on specific conditions such as time schedules or calendar events.

The flaw stems from two underlying weaknesses: Allocation of Resources Without Limits or Throttling (CWE-770) and Incorrect Default Permissions (CWE-276). When an attacker creates a large number of AutomaticZenRule objects, the system fails to properly limit resource allocation, leading to exhaustion. This resource exhaustion condition prevents the Android system from properly persisting permission settings, creating a window where permission checks can be bypassed.

The attack requires local access to the device but does not necessitate elevated privileges to initiate. Once triggered, the resource exhaustion causes the permission persistence mechanism to fail, allowing the attacker to gain elevated privileges that would normally be restricted.

Root Cause

The root cause of CVE-2022-20456 is the lack of proper resource allocation limits within the AutomaticZenRule implementation. The Android framework does not adequately restrict the number of AutomaticZenRule objects that can be created, nor does it implement proper throttling mechanisms. Combined with incorrect default permission handling (CWE-276), this allows the creation of excessive rule objects that exhaust system resources. When the system runs out of resources to track and persist permission states, the permission enforcement mechanism fails, enabling privilege escalation.

Attack Vector

The attack exploits the local access vector where a malicious application installed on the device can programmatically create numerous AutomaticZenRule objects through the Android NotificationManager API. The attack proceeds as follows:

1. A malicious application requests the ability to manage DND rules through standard Android APIs
2. The application rapidly creates a large volume of AutomaticZenRule objects
3. The excessive object creation exhausts system resources allocated for permission persistence
4. As the system struggles to maintain permission states, the persistence mechanism fails
5. The attacker's application gains elevated privileges that bypass normal permission checks

Since no user interaction is required and the attack can be launched from a standard application without special execution privileges, this vulnerability presents a significant risk for devices running affected Android versions.

Detection Methods for CVE-2022-20456

Indicators of Compromise

• Unusual number of AutomaticZenRule objects created on the device
• Abnormal memory consumption by system services, particularly the NotificationManager
• Permission-related errors or failures in Android system logs
• Unexpected privilege escalation events from non-system applications

Detection Strategies

• Monitor system logs for resource exhaustion warnings related to AutomaticZenRule or NotificationManager services
• Implement application behavioral analysis to detect apps creating excessive DND rules
• Deploy endpoint protection solutions capable of detecting anomalous system service behavior on Android devices
• Review installed applications for unusual permission requests related to DND management

Monitoring Recommendations

• Enable verbose logging for the Android framework's notification and DND subsystems
• Monitor for applications making rapid, repeated API calls to create notification rules
• Implement alerts for abnormal resource consumption patterns on managed Android devices
• Utilize mobile threat defense solutions to monitor for exploitation attempts

How to Mitigate CVE-2022-20456

Immediate Actions Required

• Update all affected Android devices to the January 2023 security patch level or later
• Remove or disable untrusted third-party applications from affected devices
• Enable Google Play Protect to detect potentially harmful applications
• Consider implementing Mobile Device Management (MDM) policies to enforce security updates

Patch Information

Google has addressed this vulnerability in the Android Security Bulletin January 2023. The patch introduces proper resource allocation limits for AutomaticZenRule objects and fixes the permission persistence mechanism to prevent privilege escalation through resource exhaustion. The vulnerability is tracked under Android ID A-242703780.

Organizations should ensure all managed Android devices are updated to security patch level 2023-01-01 or later. The patch is distributed through standard Android update channels, including OTA updates from device manufacturers and carriers.

Workarounds

• Restrict installation of applications from unknown sources on affected devices
• Implement application allowlisting on managed devices to prevent unauthorized application installation
• Use mobile threat defense solutions to monitor for malicious application behavior
• Consider network-level controls to detect and block communication from compromised devices
• Regularly audit installed applications and remove unnecessary or suspicious apps

# Verify Android security patch level via ADB
adb shell getprop ro.build.version.security_patch
# Expected output should be 2023-01-01 or later

# List installed packages to audit for suspicious applications
adb shell pm list packages -3