CVE-2021-39651 in Android
Summary
by MITRE • 12/15/2021
In TBD of TBD, there is a possible way to access PIN protected settings bypassing PIN confirmation due to a missing permission check. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android kernelAndroid ID: A-193438173References: N/A
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Analysis
by VulDB Data Team • 12/18/2021
The vulnerability identified as CVE-2021-39651 represents a critical security flaw within the Android kernel that undermines the integrity of PIN-protected settings mechanisms. This issue stems from a fundamental missing permission check that allows unauthorized access to protected system configurations. The vulnerability specifically affects the Android kernel component and was tracked under Android ID A-193438173, highlighting its significance within the Android security framework. The flaw exists in the way the system validates access permissions for PIN-protected settings, creating a pathway for privilege escalation without requiring any additional execution privileges or user interaction.
The technical implementation of this vulnerability demonstrates a failure in the kernel's access control mechanisms, where the system fails to properly verify whether a requesting process has the appropriate authorization level to access PIN-protected configurations. This missing permission check creates a direct attack vector that can be exploited by malicious processes running with standard user privileges. The flaw operates at the kernel level, making it particularly dangerous as it bypasses higher-level security controls and directly impacts the system's core security architecture. The absence of proper validation means that any process capable of interacting with the affected kernel interface can potentially access protected settings without proper PIN confirmation.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables local privilege escalation without requiring additional attack vectors or user interaction. This means that an attacker with minimal privileges can leverage this flaw to gain elevated access rights within the system, potentially leading to complete system compromise. The vulnerability's exploitation does not require any specialized tools or complex attack chains, making it particularly dangerous in environments where multiple applications or processes might be running with varying privilege levels. The lack of user interaction requirement significantly increases the attack surface and reduces the barriers to successful exploitation.
From a security standards perspective, this vulnerability aligns with CWE-284 (Improper Access Control) and represents a classic case of insufficient authorization checks within kernel space. The flaw also maps to ATT&CK technique T1068 (Local Privilege Escalation) and potentially T1547 (Registry Run Keys) if the exploited settings relate to system startup configurations. The vulnerability's nature suggests it may also fall under ATT&CK's T1059 (Command and Scripting Interpreter) if exploitation involves executing commands through the compromised interfaces. Organizations should consider implementing immediate mitigations including kernel updates, permission reviews, and enhanced monitoring of kernel access patterns to prevent exploitation of this vulnerability.
The remediation approach for CVE-2021-39651 requires systematic kernel-level patching and permission validation enhancements. System administrators should prioritize applying the latest Android kernel updates that address this specific permission check deficiency. Additionally, implementing comprehensive monitoring solutions that track kernel-level access to PIN-protected interfaces can help detect potential exploitation attempts. The vulnerability's classification as a local privilege escalation issue necessitates careful review of existing security policies and access control configurations to prevent unauthorized processes from leveraging this flaw. Organizations should also consider implementing runtime protection mechanisms that can detect and block unauthorized kernel interface access attempts, particularly those attempting to bypass PIN confirmation requirements.