CVE-2021-39694 in Android
Summary
by MITRE • 03/16/2022
In parse of RoleParser.java, there is a possible way for default apps to get permissions explicitly denied by the user due to a permissions bypass. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android-12Android ID: A-202312327
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Analysis
by VulDB Data Team • 03/20/2022
The vulnerability identified as CVE-2021-39694 resides within the Android operating system's permission handling mechanism, specifically within the RoleParser.java component responsible for parsing role assignments and permission configurations. This flaw represents a critical security weakness that undermines the fundamental principle of user consent in permission management, where applications that should be restricted from certain capabilities can bypass these restrictions through a flaw in the role parsing logic. The vulnerability affects Android 12 and is tracked under Android ID A-202312327, indicating its severity and the need for immediate attention from device manufacturers and security teams.
The technical implementation of this vulnerability stems from how the Android system processes role assignments and permission denials within the parsing logic of the RoleParser.java file. When a user explicitly denies permissions to default applications, the system should enforce these denials strictly. However, the parsing mechanism contains a logic flaw that allows default applications to bypass these explicit denials and obtain permissions they should not have access to. This occurs during the role assignment parsing phase where the system fails to properly validate or enforce the user's explicit permission denials against default application roles, creating a pathway for unauthorized privilege escalation.
The operational impact of this vulnerability is severe as it enables local privilege escalation without requiring any additional execution privileges or user interaction for exploitation. Attackers can leverage this flaw to gain elevated privileges on devices running affected Android versions, potentially allowing them to access sensitive data, modify system configurations, or escalate their access to other applications and system resources. The lack of user interaction requirement makes this vulnerability particularly dangerous as it can be exploited automatically without the user's knowledge or consent, representing a significant threat to device security and user privacy.
This vulnerability maps directly to CWE-284 Access Control Bypass, which describes scenarios where a system fails to properly enforce access controls, allowing unauthorized access to resources or capabilities. The flaw also aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation' where adversaries leverage system vulnerabilities to gain higher privileges. Additionally, the vulnerability demonstrates characteristics of T1547.001 'Registry Run Keys / Startup Folder' in that it allows for unauthorized modification of system-level permissions and access controls. The security implications extend beyond simple permission bypass to potentially enable full system compromise through the exploitation of this privilege escalation vector.
Mitigation strategies for this vulnerability should focus on immediate patch deployment through official Android security updates, as manufacturers need to provide timely fixes to address the role parsing logic flaw. Organizations should also implement monitoring for unauthorized permission changes and maintain regular security assessments to detect potential exploitation attempts. Device administrators should consider implementing additional security controls such as application blacklisting, enhanced permission monitoring, and regular security audits to prevent unauthorized privilege escalation. The fix should involve strengthening the RoleParser.java component to properly validate and enforce user-denied permissions against default application roles, ensuring that explicit user consent cannot be bypassed through parsing logic flaws.