CVE-2021-39798
📋 TL;DR
This vulnerability allows arbitrary code execution through a missing bounds check in Android's Bitmap processing. It affects Android 12 and 12L devices, enabling local privilege escalation without requiring user interaction. Attackers can gain elevated system privileges from a standard user context.
💻 Affected Systems
- Android
📦 What is this software?
Android by Google
Android by Google
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise with system-level privileges, allowing installation of persistent malware, data theft, and bypassing all security controls.
Likely Case
Local privilege escalation enabling access to protected system resources, sensitive user data, and ability to install malicious apps with elevated permissions.
If Mitigated
Limited impact if devices are fully patched and have additional security controls like SELinux enforcing mode and app sandboxing.
🎯 Exploit Status
Exploitation requires local access and knowledge of memory layout. No public exploit code is known, but the vulnerability is well-documented.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Android Security Bulletin April 2022 patches
Vendor Advisory: https://source.android.com/security/bulletin/2022-04-01
Restart Required: Yes
Instructions:
1. Apply April 2022 Android security patch. 2. Update device through Settings > System > System update. 3. For enterprise devices, push updates through MDM solution. 4. Verify patch installation.
🔧 Temporary Workarounds
Restrict app installations
androidPrevent installation of untrusted apps that could exploit this vulnerability
Enable Google Play Protect
androidUse Google's built-in malware protection to detect malicious apps
🧯 If You Can't Patch
- Isolate affected devices from sensitive networks and data
- Implement strict app whitelisting and disable unknown sources
🔍 How to Verify
Check if Vulnerable:
Check Android version in Settings > About phone > Android version. If version is 12 or 12L without April 2022 security patch, device is vulnerable.Check Version:
adb shell getprop ro.build.version.release && adb shell getprop ro.build.version.security_patchVerify Fix Applied:
Verify Android version is patched with April 2022 security update in Settings > About phone > Android security patch level.📡 Detection & Monitoring
Log Indicators:
- Unusual process privilege escalation
- SELinux denials related to Bitmap operations
- Crash reports from system_server
Network Indicators:
- Unusual outbound connections from system processes
SIEM Query:
source="android_logs" AND (process_privilege_change OR selinux_denial OR "Bitmap_createFromParcel")