CVE-2021-39651
📋 TL;DR
This Android kernel vulnerability allows local attackers to bypass PIN protection on device settings without requiring user interaction. It enables privilege escalation from a standard user to higher privileges, affecting Android devices with vulnerable kernel versions. The exploit requires physical or local access to the device.
💻 Affected Systems
- Android devices with vulnerable kernel
📦 What is this software?
Android by Google
⚠️ Risk & Real-World Impact
Worst Case
Attacker gains full control over device settings, potentially enabling further privilege escalation, data theft, or persistence mechanisms.
Likely Case
Unauthorized access to PIN-protected settings allowing configuration changes, security bypass, or privacy violations.
If Mitigated
Limited impact with proper device access controls, but still represents a security boundary violation.
🎯 Exploit Status
Exploitation requires local access but no user interaction. Missing permission check makes exploitation straightforward once access is obtained.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: December 2021 Android Security Bulletin patches
Vendor Advisory: https://source.android.com/security/bulletin/pixel/2021-12-01
Restart Required: Yes
Instructions:
1. Check for Android system updates in Settings > System > System update. 2. Install December 2021 security patch or later. 3. Reboot device after installation.
🔧 Temporary Workarounds
Restrict physical device access
allImplement strict physical security controls to prevent unauthorized local access to devices.
Enable additional authentication layers
androidUse biometric authentication or additional PINs for sensitive settings where available.
🧯 If You Can't Patch
- Implement Mobile Device Management (MDM) with strict access controls
- Isolate vulnerable devices from sensitive networks and data
🔍 How to Verify
Check if Vulnerable:
Check Android security patch level in Settings > About phone > Android version. If patch level is earlier than December 2021, device is likely vulnerable.Check Version:
adb shell getprop ro.build.version.security_patchVerify Fix Applied:
Verify security patch level shows December 2021 or later in Settings > About phone > Android version.📡 Detection & Monitoring
Log Indicators:
- Unexpected settings changes without PIN prompts
- Permission denial logs for settings access attempts
Network Indicators:
- None - local exploit only
SIEM Query:
Look for Android device logs showing settings modifications without corresponding authentication events.