CVE-2021-39660 in Android
Summary
by MITRE • 12/13/2022
In TBD of TBD, there is a possible way to archive arbitrary code execution in kernel due to a race condition. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android SoCAndroid ID: A-254742984
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 04/23/2025
The vulnerability identified as CVE-2021-39660 represents a critical race condition flaw within the Android kernel implementation that enables local privilege escalation without requiring any additional privileges or user interaction. This vulnerability resides in the kernel-level code execution path and specifically affects Android System-on-Chip implementations. The race condition occurs during a critical section of code execution where multiple threads or processes can simultaneously access shared resources without proper synchronization mechanisms. Such conditions are particularly dangerous in kernel space as they can be exploited to gain unauthorized access to privileged operations that should normally be restricted to system-level processes only. The vulnerability's classification as a local escalation of privilege means that an attacker with minimal privileges can leverage this flaw to elevate their access level to that of the kernel itself.
The technical implementation of this race condition involves a timing window where the kernel fails to properly validate state transitions or resource access during concurrent operations. According to CWE standards, this vulnerability maps to CWE-367 which describes Time-of-Check to Time-of-Use (TOCTOU) flaws, though the specific nature here appears to be a more generalized race condition that allows for code execution rather than just privilege escalation through file access manipulation. The flaw likely occurs in kernel memory management or process scheduling components where improper locking mechanisms permit malicious code to manipulate kernel data structures or function pointers during the execution window. This type of vulnerability is particularly insidious because it operates at the kernel level where all system operations are subject to the attacker's control once the privilege escalation is achieved.
From an operational impact perspective, this vulnerability poses significant risk to Android devices as it allows for complete system compromise without requiring any user interaction or additional privileges. The exploitation process would involve a local attacker who can execute code within the system to manipulate the race condition timing and gain kernel-level access. This capability directly maps to ATT&CK technique T1068 which describes "Local Privilege Escalation" and specifically addresses kernel exploits. The vulnerability affects Android SoC implementations, meaning that all devices utilizing these specific chipsets are potentially vulnerable, regardless of the Android version or security patch level. This makes the impact particularly widespread across the Android ecosystem, as many devices share common SoC architectures and may not receive timely security updates.
Mitigation strategies for this vulnerability require immediate patching of the affected kernel implementations through Android security updates. Organizations should prioritize deployment of patches that address the specific race condition in kernel memory management or process synchronization components. The recommended approach involves implementing proper mutex or semaphore locking mechanisms to prevent concurrent access to shared resources during critical operations. Additionally, kernel hardening techniques such as stack canaries, kernel address space layout randomization, and code integrity checks should be enabled to provide additional layers of protection. System administrators should also monitor for any anomalous kernel-level activity that might indicate exploitation attempts, as the vulnerability allows for complete system compromise without user interaction. The patching process should be coordinated across all affected Android devices and SoC manufacturers to ensure comprehensive protection against this kernel-level race condition vulnerability.