CVE-2021-39738 in Android
Summary
by MITRE • 05/11/2022
In CarSetings, there is a possible to pair BT device bypassing user's consent 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-10 Android-11 Android-12 Android-12LAndroid ID: A-216190509
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Analysis
by VulDB Data Team • 05/13/2022
The vulnerability identified as CVE-2021-39738 resides within the CarSettings component of Android operating systems spanning versions 10 through 12L, representing a critical security flaw that undermines the fundamental principles of user consent and privilege management. This issue manifests specifically within the Bluetooth pairing mechanism where the system fails to enforce proper permission validation before establishing device connections. The flaw operates at the system level where Bluetooth pairing functionality is exposed without adequate authorization checks, creating a pathway for malicious actors to bypass the intended user consent process that should normally be required for device pairing operations.
The technical implementation of this vulnerability stems from a missing permission check within the CarSettings service that handles Bluetooth device pairing operations. When a Bluetooth device attempts to pair with a vehicle system, the underlying code does not properly validate whether the pairing request originates from an authorized source or if appropriate user consent has been obtained through the standard Android permission framework. This absence of permission verification creates a direct bypass mechanism that allows unauthorized pairing operations to proceed without the necessary user interaction or explicit authorization typically required for such sensitive operations. The vulnerability is classified under CWE-652 Improper Neutralization of Special Elements used in a Code Context, specifically relating to insufficient authorization checks in system-level services.
From an operational perspective, this vulnerability presents a severe risk of local privilege escalation without requiring any additional execution privileges or user interaction for exploitation. Attackers can leverage this flaw to establish Bluetooth connections with vehicle systems without user consent, potentially gaining access to sensitive vehicle data, control functions, or communication channels that should remain protected. The impact extends beyond simple pairing bypass as it represents a fundamental breakdown in Android's security model where system-level services fail to enforce proper access controls. This vulnerability aligns with ATT&CK technique T1068 Exploitation for Privilege Escalation, where an attacker can exploit a weakness in system permissions to gain elevated privileges within the vehicle's operating environment.
The implications of this vulnerability are particularly concerning given the critical nature of vehicle connectivity systems and the potential for unauthorized access to vehicle control functions. An attacker with physical access to the vehicle system or remote exploitation capabilities could potentially establish persistent Bluetooth connections that allow for ongoing monitoring or control of vehicle functions. The lack of user interaction requirement means that exploitation can occur silently in the background without any warning to the vehicle operator. This vulnerability represents a significant risk to automotive cybersecurity and demonstrates the importance of proper permission handling in system services that interface with critical vehicle functions. The Android security model relies heavily on proper permission enforcement, and this flaw undermines the foundational security assumptions that protect users from unauthorized access to their vehicle's digital systems. Mitigation efforts should focus on implementing proper permission validation within the CarSettings service and ensuring that all Bluetooth pairing operations require explicit user consent through the established Android permission framework.