CVE-2018-9476 in Android
Summary
by MITRE
In avrc_pars_browsing_cmd of avrc_pars_tg.cc, there is a possible use-after-free due to improper locking. This could lead to remote escalation of privilege in the Bluetooth service with no additional execution privileges needed. User interaction is not needed for exploitation. Product: Android Versions: Android-8.0 Android-8.1 Android ID: A-109699112
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Analysis
by VulDB Data Team • 03/29/2020
The vulnerability identified as CVE-2018-9476 represents a critical use-after-free condition within the Bluetooth AVRCP (Audio Video Remote Control Profile) implementation of Android 8.0 and 8.1 operating systems. This flaw exists in the avrc_pars_browsing_cmd function located in the avrc_pars_tg.cc source file, which handles Bluetooth browsing commands. The issue arises from inadequate synchronization mechanisms and improper locking protocols during the processing of Bluetooth AVRCP browsing commands, creating a scenario where memory that has been freed can still be accessed by subsequent operations.
The technical exploitation of this vulnerability leverages the improper locking mechanism to trigger a use-after-free condition, where an attacker can manipulate the Bluetooth service to access memory that has already been deallocated. This memory corruption vulnerability allows for arbitrary code execution within the Bluetooth service context, which operates with elevated privileges. The vulnerability is particularly concerning because it enables remote privilege escalation without requiring any user interaction or additional execution privileges, making it highly dangerous in both targeted and opportunistic attack scenarios. The flaw specifically affects the Bluetooth service's handling of browsing commands, which are commonly used in audio streaming and media control applications.
From an operational impact perspective, this vulnerability provides attackers with a pathway to achieve full system compromise through Bluetooth communication alone. The attack surface is extensive as Bluetooth is enabled by default on most Android devices and frequently used for audio streaming, media control, and device pairing operations. An attacker positioned within Bluetooth range of a vulnerable device can exploit this vulnerability to execute malicious code with system-level privileges, potentially gaining access to sensitive user data, controlling device functions, or establishing persistent access. The lack of user interaction requirements means that the attack can be automated and executed silently, making it particularly dangerous for mobile devices that are constantly connected to Bluetooth networks.
The vulnerability aligns with CWE-416, which specifically addresses use-after-free conditions, and represents a significant weakness in Android's Bluetooth security implementation. According to ATT&CK framework, this vulnerability maps to T1059.007 for command and scripting interpreter and T1068 for exploit for privilege escalation, as the flaw enables remote code execution with elevated privileges. The issue demonstrates poor memory management practices and inadequate thread synchronization in the Bluetooth service implementation, which violates security best practices for protecting against memory corruption vulnerabilities. Organizations should implement immediate mitigations including applying the relevant Android security patches, disabling Bluetooth when not in use, and monitoring for suspicious Bluetooth activity. The vulnerability also highlights the importance of proper locking mechanisms in multi-threaded environments and demonstrates how seemingly minor implementation flaws in system services can lead to critical privilege escalation exploits.