CVE-2021-39743 in Android
Summary
by MITRE • 03/30/2022
In PackageManager, there is a possible way to update the last usage time of another package 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-12LAndroid ID: A-201534884
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Analysis
by VulDB Data Team • 04/02/2022
The vulnerability identified as CVE-2021-39743 resides within the Android PackageManager component, specifically addressing a critical permission oversight that enables unauthorized privilege escalation. This flaw exists in Android 12L and represents a significant security weakness in the operating system's permission model. The vulnerability stems from the PackageManager's failure to properly validate permissions when updating package usage statistics, creating an avenue for malicious actors to manipulate the last usage time of arbitrary applications.
The technical implementation of this vulnerability involves a missing permission check within the PackageManager's usage tracking mechanism. When applications attempt to update package usage timestamps, the system should verify that the requesting process has appropriate authorization to modify another package's metadata. However, this validation step is absent, allowing any local process to modify usage times of packages they do not own. This represents a direct violation of Android's security model where each application should only have access to its own resources and metadata.
From an operational perspective, this vulnerability enables local privilege escalation without requiring any additional execution privileges or user interaction for exploitation. An attacker with local access to an Android device can leverage this flaw to manipulate package usage statistics, potentially affecting system behavior, app recommendations, or even bypassing certain security mechanisms that rely on accurate usage timing. The lack of user interaction requirement makes this particularly dangerous as it can be exploited automatically without any user awareness or consent.
The impact of this vulnerability extends beyond simple metadata manipulation, as package usage times are often used by the Android system for various operational purposes including app optimization, battery management, and security monitoring. By manipulating these timestamps, an attacker could potentially influence how the system manages resources or how it responds to security threats. This flaw aligns with CWE-284, which addresses improper access control, and maps to ATT&CK technique T1068, which covers local privilege escalation through system-level vulnerabilities.
Mitigation strategies for this vulnerability require immediate patching of affected Android versions, particularly Android 12L where the flaw was identified. System administrators and device manufacturers should prioritize deployment of security updates that implement proper permission checks within the PackageManager component. Additionally, organizations should conduct security audits to identify any applications or processes that might be exploiting this vulnerability and implement monitoring for anomalous package usage time modifications. The fix should enforce strict permission validation before allowing any package usage time updates, ensuring that only authorized processes can modify metadata for other applications.