CVE-2021-0435
📋 TL;DR
This vulnerability allows remote attackers to leak uninitialized heap memory from Android devices via Bluetooth AVRCP protocol without user interaction. It affects Android devices running versions 8.1 through 11. Attackers can potentially access sensitive data from device memory.
💻 Affected Systems
- Android devices with Bluetooth capability
📦 What is this software?
Android by Google
Android by Google
Android by Google
Android by Google
⚠️ Risk & Real-World Impact
Worst Case
Remote attacker extracts sensitive information like authentication tokens, encryption keys, or personal data from device memory without any user interaction.
Likely Case
Information disclosure of random heap data, potentially including application data or system information that could aid further attacks.
If Mitigated
No impact if patched or Bluetooth is disabled; limited impact if device is not discoverable or paired with untrusted devices.
🎯 Exploit Status
Exploitation requires Bluetooth proximity and knowledge of the vulnerability, but no authentication or user interaction.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Android Security Patch Level 2021-04-01 or later
Vendor Advisory: https://source.android.com/security/bulletin/2021-04-01
Restart Required: Yes
Instructions:
1. Check for system updates in Settings > System > Advanced > System update. 2. Install Android Security Patch Level 2021-04-01 or later. 3. Reboot device after installation.
🔧 Temporary Workarounds
Disable Bluetooth
androidTurn off Bluetooth to prevent exploitation via AVRCP protocol
adb shell settings put global bluetooth_on 0
Settings > Connected devices > Connection preferences > Bluetooth > Toggle off
Limit Bluetooth Visibility
androidSet Bluetooth to non-discoverable mode to reduce attack surface
adb shell settings put global bluetooth_discoverability 0
Settings > Connected devices > Connection preferences > Bluetooth > Device name > Turn off 'Make device discoverable'
🧯 If You Can't Patch
- Disable Bluetooth when not in use, especially in untrusted environments
- Implement network segmentation to isolate vulnerable devices from critical systems
🔍 How to Verify
Check if Vulnerable:
Check Android version and security patch level: Settings > About phone > Android version & Security patch level. If version is 8.1-11 and patch level is before 2021-04-01, device is vulnerable.Check Version:
adb shell getprop ro.build.version.release && adb shell getprop ro.build.version.security_patchVerify Fix Applied:
Verify security patch level is 2021-04-01 or later in Settings > About phone > Security patch level.📡 Detection & Monitoring
Log Indicators:
- Unusual Bluetooth AVRCP protocol activity in Android system logs
- Multiple failed or abnormal AVRCP command attempts
Network Indicators:
- Suspicious Bluetooth traffic patterns targeting AVRCP services
SIEM Query:
source="android_system" AND (process="bluetooth" OR "avrc") AND (event="vendor_command" OR "uninitialized")