CVE-2019-2121 in Android
Summary
by MITRE
In ActivityManagerService.attachApplication of ActivityManagerService, there is a possible race condition. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation. Product: Android. Versions: Android-9. Android ID: A-131105245.
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Analysis
by VulDB Data Team • 08/01/2020
The vulnerability identified as CVE-2019-2121 represents a critical race condition flaw within the Android operating system's ActivityManagerService component. This race condition exists in the attachApplication method of ActivityManagerService, which is responsible for managing application lifecycle and process attachment within the Android framework. The vulnerability is particularly concerning because it allows for local privilege escalation without requiring any additional execution privileges or user interaction, making it a significant security risk for Android devices running version 9.0.
The technical nature of this race condition stems from improper synchronization mechanisms within the ActivityManagerService implementation. When an application attempts to attach to the system, the service handles this process through multiple threads and operations that are not adequately protected against concurrent access. This lack of proper locking mechanisms creates a window where malicious code can exploit the timing gap between operations to manipulate system state. The vulnerability falls under CWE-362, which specifically addresses race conditions in software implementations where multiple threads or processes access shared resources without proper synchronization.
From an operational perspective, this vulnerability enables attackers with local access to escalate their privileges from standard user level to system level without requiring any special permissions or user interaction. The exploitation process leverages the inherent timing issues in the application attachment process, allowing malicious code to manipulate the system's process management mechanisms. This privilege escalation capability means that an attacker could gain complete control over the device, potentially accessing sensitive data, modifying system files, or installing malicious applications. The absence of user interaction requirements makes this vulnerability particularly dangerous as it can be exploited automatically without any user awareness or consent.
Security professionals should consider this vulnerability in the context of the ATT&CK framework, specifically under the Privilege Escalation tactic where adversaries seek to gain higher-level permissions. The vulnerability aligns with techniques such as 'Exploitation for Privilege Escalation' and 'Process Injection' as attackers can leverage the race condition to inject malicious code into system processes. Organizations should implement immediate mitigations including applying the latest Android security patches, monitoring for suspicious process behaviors, and conducting security audits of applications that might exploit this vulnerability. The Android security team addressed this issue through proper synchronization mechanisms in subsequent updates, emphasizing the importance of thread-safe programming practices in system-level components.