CVE-2021-0688
📋 TL;DR
CVE-2021-0688 is a lock screen bypass vulnerability in Android's PhoneWindowManager due to a race condition. It allows local attackers to bypass the lock screen without user interaction, potentially gaining unauthorized access to the device. This affects Android devices running versions 8.1 through 11.
💻 Affected Systems
- Android
📦 What is this software?
Android by Google
Android by Google
Android by Google
Android by Google
⚠️ Risk & Real-World Impact
Worst Case
An attacker with physical access could bypass the lock screen and gain full access to the device, including personal data, apps, and potentially escalate privileges to system level.
Likely Case
Local attacker bypasses lock screen to access device contents, install malicious apps, or access sensitive information without authentication.
If Mitigated
With proper security updates applied, the vulnerability is eliminated and lock screen security functions as intended.
🎯 Exploit Status
Exploitation requires physical access and timing precision due to race condition nature, but no authentication or user interaction needed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Android Security Bulletin September 2021 patches
Vendor Advisory: https://source.android.com/security/bulletin/2021-09-01
Restart Required: Yes
Instructions:
1. Check for Android system updates in Settings > System > Advanced > System update. 2. Install September 2021 or later security patch. 3. Reboot device after installation.
🔧 Temporary Workarounds
Disable lock screen (not recommended)
androidRemoving lock screen eliminates the bypass vulnerability but removes device security
Settings > Security > Screen lock > None
Enable enhanced security features
androidUse biometric authentication or stronger PIN patterns to reduce attack surface
Settings > Security > Screen lock > Choose biometric or complex PIN
🧯 If You Can't Patch
- Implement strict physical security controls for devices
- Enable remote wipe capabilities and enforce device encryption
🔍 How to Verify
Check if Vulnerable:
Check Android version in Settings > About phone > Android version. If version is 8.1, 9, 10, or 11 without September 2021 patches, device is vulnerable.Check Version:
adb shell getprop ro.build.version.release && adb shell getprop ro.build.version.security_patchVerify Fix Applied:
Verify Android Security Patch Level shows September 2021 or later in Settings > About phone > Android security patch level.📡 Detection & Monitoring
Log Indicators:
- Multiple rapid lock/unlock events
- Security exceptions in system logs related to PhoneWindowManager
Network Indicators:
- None - local attack only
SIEM Query:
Search for security exceptions containing 'PhoneWindowManager' or 'lockNow' in Android system logs