CVE-2021-39801
📋 TL;DR
CVE-2021-39801 is a use-after-free vulnerability in the Android kernel's ION memory management subsystem. This allows local attackers to escalate privileges without user interaction, potentially gaining root access on affected devices. The vulnerability affects Android devices running vulnerable kernel versions.
💻 Affected Systems
- Android devices
📦 What is this software?
Android by Google
⚠️ Risk & Real-World Impact
Worst Case
Local attacker gains full root privileges, compromising the entire device, accessing all data, and potentially installing persistent malware.
Likely Case
Local malware or malicious apps escalate privileges to gain unauthorized access to system resources and sensitive data.
If Mitigated
With proper kernel hardening and SELinux policies, exploitation may be limited to specific contexts, but root access remains possible.
🎯 Exploit Status
Exploitation requires local access but no user interaction. Kernel exploitation requires understanding of memory management and race conditions.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Android security patch level 2022-04-01 or later
Vendor Advisory: https://source.android.com/security/bulletin/2022-04-01
Restart Required: Yes
Instructions:
1. Check for Android system updates in Settings > System > System update. 2. Install the April 2022 or later security patch. 3. Reboot the device. 4. For custom ROMs or kernels, apply the upstream kernel patch from the Android security bulletin.
🔧 Temporary Workarounds
Disable vulnerable ION functionality
linuxRemove or disable the vulnerable ION memory management subsystem if not required
This requires kernel configuration changes and is device-specific
🧯 If You Can't Patch
- Restrict installation of untrusted applications from unknown sources
- Implement strict SELinux policies to limit privilege escalation impact
🔍 How to Verify
Check if Vulnerable:
Check kernel version and security patch level: Settings > About phone > Android version > Security patch levelCheck Version:
adb shell getprop ro.build.version.security_patchVerify Fix Applied:
Verify security patch level is 2022-04-01 or later in device settings📡 Detection & Monitoring
Log Indicators:
- Kernel panic logs
- ION subsystem error messages in dmesg
- Unexpected privilege escalation attempts
Network Indicators:
- None - this is a local exploit
SIEM Query:
Search for kernel crash logs or privilege escalation patterns in Android device logs