CVE-2021-39668
📋 TL;DR
This vulnerability allows local privilege escalation on Android devices through an intent redirection flaw in the System UI. An attacker could trick the system into performing actions with System UI privileges, potentially accessing sensitive data or functionality. Only Android 11 and 12 devices are affected.
💻 Affected Systems
- Android
📦 What is this software?
Android by Google
Android by Google
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attacker to perform any action as System UI, including accessing sensitive user data, installing malicious apps, or modifying system settings.
Likely Case
Limited privilege escalation allowing access to some protected system functions or user data that would normally require higher permissions.
If Mitigated
No impact if patched or if user avoids installing malicious apps and granting unnecessary permissions.
🎯 Exploit Status
Requires user interaction and likely a malicious app to trigger the intent redirection. No public exploit code known.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Android Security Patch Level 2022-02-01 or later
Vendor Advisory: https://source.android.com/security/bulletin/2022-02-01
Restart Required: Yes
Instructions:
1. Check for system updates in Settings > System > System update. 2. Install Android Security Patch Level 2022-02-01 or later. 3. Restart device after installation.
🔧 Temporary Workarounds
Disable unknown sources
androidPrevent installation of apps from unknown sources to reduce attack surface
Settings > Security > Install unknown apps > Disable for all apps
Review app permissions
androidRegularly review and restrict app permissions, especially for less trusted apps
Settings > Apps > [App Name] > Permissions
🧯 If You Can't Patch
- Restrict installation of new apps and only use trusted sources like Google Play Store
- Implement mobile device management (MDM) policies to control app installations and permissions
🔍 How to Verify
Check if Vulnerable:
Check Android version and security patch level in Settings > About phone > Android versionCheck Version:
Settings > About phone > Android versionVerify Fix Applied:
Verify security patch level is 2022-02-01 or later in Settings > About phone > Android security update📡 Detection & Monitoring
Log Indicators:
- Unusual System UI activity, unexpected intent redirections in system logs
Network Indicators:
- Not applicable - local vulnerability
SIEM Query:
Not applicable for typical Android deployments