CVE-2021-0332 in Android
Summary
by MITRE • 02/10/2021
In bootFinished of SurfaceFlinger.cpp, there is a possible memory corruption due to a use after free. This could lead to local escalation of privilege with User execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android-11 Android-10Android ID: A-169256435
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 02/27/2021
The vulnerability identified as CVE-2021-0332 resides within the Android operating system's SurfaceFlinger component, specifically in the bootFinished function of SurfaceFlinger.cpp. This represents a critical memory corruption flaw that stems from a use-after-free condition, where previously freed memory locations are accessed or modified by subsequent operations. The vulnerability affects Android versions 10 and 11, with the Android ID A-169256435 documenting the specific issue. SurfaceFlinger serves as the core system component responsible for compositing graphics layers and managing the display pipeline, making it a prime target for privilege escalation attacks. The flaw occurs during the system boot process when SurfaceFlinger initializes its components, creating a window of opportunity for malicious code to exploit the memory management error.
The technical implementation of this vulnerability involves a classic use-after-free scenario where a pointer referencing freed memory is still being accessed or modified by the bootFinished function. When SurfaceFlinger completes its initialization sequence, it may attempt to access memory that has already been deallocated, leading to unpredictable behavior and potential memory corruption. This type of flaw falls under CWE-416, which specifically addresses the use of freed memory condition. The exploitation requires an attacker to already possess user execution privileges, meaning they must have the ability to run code within the Android user context. However, the memory corruption can be leveraged to execute arbitrary code with elevated privileges, potentially allowing for full system compromise.
The operational impact of CVE-2021-0332 extends beyond simple memory corruption, as it provides a pathway for local privilege escalation attacks. An attacker with user-level access can exploit this vulnerability to gain root privileges, effectively bypassing the Android security model's user and system privilege boundaries. This represents a significant threat to Android device security, particularly in environments where user accounts may be compromised or where attackers can gain initial access through other vectors. The vulnerability's exploitation does not require user interaction, making it particularly dangerous as it can be triggered automatically during the system boot process. The attack surface is further expanded by the fact that this occurs during the critical boot phase when system components are being initialized and memory management operations are actively occurring.
Mitigation strategies for this vulnerability should focus on immediate patching of affected Android versions, as Google has released security updates addressing this specific use-after-free condition. The recommended approach involves implementing proper memory management practices within the SurfaceFlinger component, including ensuring that pointers are properly invalidated after memory deallocation and adding additional validation checks before memory access operations. Organizations should also consider implementing runtime monitoring to detect anomalous memory access patterns that could indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation,' and demonstrates how memory corruption flaws can be leveraged to bypass system security controls. Additionally, defensive measures such as address space layout randomization and stack canaries can provide additional protection layers against exploitation attempts, though the primary solution remains the implementation of proper memory management within the affected Android components.