CVE-2021-0923
📋 TL;DR
This vulnerability in Android's permission system allows local attackers to escalate privileges without user interaction. It affects Android 12 devices where a missing permission check in Permission.java could let malicious apps gain internal permissions they shouldn't have access to.
💻 Affected Systems
- Android
📦 What is this software?
Android by Google
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise where an attacker gains full system-level access, potentially installing persistent malware, accessing all user data, and controlling device functions.
Likely Case
Local privilege escalation allowing malicious apps to access sensitive system permissions, user data, or other apps' protected resources without proper authorization.
If Mitigated
Limited impact if devices are patched, have strict app vetting, or use security software that detects permission abuse attempts.
🎯 Exploit Status
Exploitation requires a malicious app to be installed first. The vulnerability itself doesn't require authentication or user interaction once the app is installed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Android Security Patch Level 2021-11-01 or later
Vendor Advisory: https://source.android.com/security/bulletin/2021-11-01
Restart Required: Yes
Instructions:
1. Check for system updates in Settings > System > System update. 2. Install the November 2021 Android security patch or later. 3. Restart the device after installation. 4. Verify the patch level in Settings > About phone > Android version.
🔧 Temporary Workarounds
Restrict app installations
androidPrevent installation of apps from unknown sources to reduce attack surface
Use verified boot
androidEnsure verified boot is enabled to detect system modifications
🧯 If You Can't Patch
- Isolate affected devices from sensitive networks and data
- Implement mobile device management with strict app whitelisting
🔍 How to Verify
Check if Vulnerable:
Check Android version in Settings > About phone > Android version. If it shows Android 12 without November 2021 security patch, the device is vulnerable.Check Version:
adb shell getprop ro.build.version.release && adb shell getprop ro.build.version.security_patchVerify Fix Applied:
Verify the security patch level in Settings > About phone > Android version. Look for 'Security patch level: November 5, 2021' or later.📡 Detection & Monitoring
Log Indicators:
- Unusual permission requests in system logs
- Apps attempting to access protected permissions without proper checks
Network Indicators:
- None - this is a local privilege escalation
SIEM Query:
Look for Android system logs showing permission escalation attempts or unusual permission grants