CVE-2021-0684 in Android
Summary
by MITRE • 10/06/2021
In TouchInputMapper::sync of TouchInputMapper.cpp, there is a possible out of bounds write due to a use after free. 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-8.1 Android-9Android ID: A-179839665
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 10/10/2021
The vulnerability identified as CVE-2021-0684 resides within the TouchInputMapper component of Android's input handling system, specifically in the sync method of TouchInputMapper.cpp. This flaw represents a critical security issue that exploits a use-after-free condition, where memory that has been freed is still being accessed or written to by the application. The vulnerability affects multiple Android versions including Android 8.1, 9, 10, and 11, indicating a widespread impact across the Android ecosystem. The use-after-free condition occurs when the TouchInputMapper attempts to synchronize touch input data while a memory allocation has already been released, creating a scenario where subsequent operations may write data to memory that is no longer valid for the intended purpose.
The technical nature of this vulnerability stems from improper memory management within the input subsystem, which is a fundamental component responsible for processing touch events from various input devices. When the sync method executes, it likely accesses pointers that reference freed memory locations, potentially allowing an attacker to manipulate the memory layout through controlled input operations. This type of flaw falls under CWE-416 which specifically addresses use-after-free vulnerabilities, where a program continues to use a pointer after the memory it points to has been freed. The vulnerability's exploitation does not require user interaction, making it particularly dangerous as it can be triggered automatically during normal device operation. The attack vector involves manipulating touch input events to cause the system to write data beyond the bounds of allocated memory, potentially overwriting critical system structures or code segments.
The operational impact of CVE-2021-0684 extends to local privilege escalation, meaning an attacker with minimal privileges could potentially elevate their access level within the Android operating system. This escalation capability arises because the vulnerability allows for memory corruption that could be leveraged to execute arbitrary code with higher privileges. The attack surface is broad since touch input is fundamental to Android device operation, and any application or system component that processes touch events could potentially be exploited. The vulnerability's classification as a local privilege escalation means that it does not require network connectivity or complex user interaction, making it particularly concerning for mobile device security. The exploitation could potentially allow attackers to gain root access to the device, compromising the entire system and all stored data.
Mitigation strategies for CVE-2021-0684 primarily focus on applying the security patches released by Google as part of their regular Android security updates. Users should ensure their devices are running the latest Android versions that include fixes for this vulnerability. System administrators should prioritize patch deployment across enterprise devices to prevent potential exploitation. The vulnerability's nature suggests that defensive programming techniques such as proper memory management, null pointer checks, and bounds verification should be implemented in the input handling subsystem. Additionally, implementing runtime protections such as address space layout randomization and stack canaries could help mitigate the impact of similar memory corruption vulnerabilities. Organizations should also consider monitoring for unusual touch input patterns that might indicate exploitation attempts, though the lack of user interaction requirement makes this challenging. The vulnerability aligns with ATT&CK technique T1068 which involves exploiting legitimate credentials or privileges, as the escalation occurs through legitimate system components that are part of normal Android operation.