CVE-2021-0889 Overview
CVE-2021-0889 is a critical remote code execution vulnerability affecting Android TV devices. The vulnerability exists due to a lack of rate limiting in the pairing flow, which allows attackers to perform silent pairing with target devices. This flaw enables remote code execution without requiring any additional execution privileges or user interaction, making it particularly dangerous for Android TV deployments.
Critical Impact
Remote attackers can achieve code execution on Android TV devices through silent pairing without any user interaction required.
Affected Products
- Google Android TV 8.1
- Google Android TV 9.0
- Google Android TV 10.0
- Google Android TV 11.0
- Google Android TV 12.0
Discovery Timeline
- 2021-12-15 - CVE-2021-0889 published to NVD
- 2024-11-21 - Last updated in NVD database
Technical Details for CVE-2021-0889
Vulnerability Analysis
This vulnerability resides in the Android TV pairing mechanism, which is designed to allow remote controls and other devices to connect to Android TV systems. The core issue stems from the absence of rate limiting controls during the pairing authentication process.
Under normal operation, when a device attempts to pair with an Android TV, there should be safeguards in place to prevent brute-force attacks or automated pairing attempts. However, due to this flaw, an attacker on the same network can repeatedly attempt pairing operations without encountering any throttling or lockout mechanisms.
The vulnerability is particularly severe because it requires no user interaction for exploitation. An attacker can silently establish a pairing connection to the Android TV device, effectively gaining control over the system. Once paired, the attacker can execute arbitrary code with the same privileges as the TV system, potentially leading to complete device compromise.
Root Cause
The root cause of CVE-2021-0889 is the missing rate limiting implementation in the Android TV pairing flow. The pairing protocol fails to implement proper controls that would detect and block repeated or automated pairing attempts. This design flaw allows attackers to bypass the intended security model of the pairing mechanism through brute-force techniques or by exploiting the unprotected pairing sequence to achieve silent device pairing.
Attack Vector
The attack vector for this vulnerability is network-based, meaning an attacker must have network access to the target Android TV device. The exploitation process involves:
- Network Reconnaissance: The attacker identifies Android TV devices on the local network
- Pairing Exploitation: The attacker initiates multiple pairing requests without being rate-limited
- Silent Pairing: Due to the lack of controls, the attacker successfully pairs with the device without user notification
- Code Execution: Once paired, the attacker can execute arbitrary commands on the Android TV device
The attack does not require authentication, privileges, or user interaction, which significantly lowers the barrier for exploitation. Attackers with network proximity to vulnerable Android TV devices can leverage this vulnerability to gain unauthorized access and execute malicious code.
Detection Methods for CVE-2021-0889
Indicators of Compromise
- Unusual or unexpected device pairing events in Android TV system logs
- Multiple rapid pairing attempts from unknown MAC addresses or IP addresses
- Unauthorized paired devices appearing in the Android TV paired devices list
- Unexpected network connections originating from Android TV devices
Detection Strategies
- Monitor network traffic for anomalous pairing protocol activity targeting Android TV devices
- Implement network intrusion detection rules to identify brute-force pairing attempts
- Review Android TV device logs for pairing events that were not initiated by authorized users
- Deploy endpoint detection solutions capable of monitoring Android-based systems for suspicious activity
Monitoring Recommendations
- Enable verbose logging on Android TV devices to capture pairing-related events
- Implement network segmentation to isolate IoT and entertainment devices from critical network segments
- Regularly audit paired devices on Android TV systems and remove unrecognized entries
- Deploy network monitoring solutions to detect unusual traffic patterns to and from Android TV devices
How to Mitigate CVE-2021-0889
Immediate Actions Required
- Update all affected Android TV devices to the latest available firmware version
- Review and remove any unrecognized paired devices from Android TV systems
- Implement network segmentation to restrict access to Android TV devices
- Consider disabling remote pairing functionality if not required for operations
Patch Information
Google has addressed this vulnerability in the Android Security Bulletin for November 2021. Administrators should apply the security updates provided by their device manufacturers. The vulnerability is tracked internally by Google as Android ID: A-180745296. For detailed patch information and update instructions, refer to the Android Security Bulletin November 2021.
Workarounds
- Isolate Android TV devices on a separate network VLAN with restricted access
- Disable remote pairing features when not actively needed for legitimate device connections
- Implement firewall rules to limit which devices can initiate connections to Android TV systems
- Monitor paired device lists regularly and investigate any unexpected entries
# Network isolation example - restrict Android TV to specific VLAN
# Configure firewall rules to limit pairing access
iptables -A INPUT -p tcp --dport 6466 -s 192.168.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 6466 -j DROP
# Review connected devices on Android TV (via ADB)
adb shell dumpsys bluetooth_manager | grep -A 5 "Bonded devices"
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
