CVE-2021-1028 in Android
Summary
by MITRE • 12/15/2021
In setClientStateLocked of SurfaceFlinger.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-12Android ID: A-193034683
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 12/22/2021
The vulnerability identified as CVE-2021-1028 resides within the Android system's SurfaceFlinger component, which serves as the core graphics compositor responsible for managing display surfaces and rendering operations across the device. This flaw manifests in the setClientStateLocked function within SurfaceFlinger.cpp, representing a critical security weakness that could potentially enable local privilege escalation without requiring any additional execution privileges or user interaction for exploitation. The vulnerability specifically involves a use-after-free condition that occurs during the management of client state within the graphics subsystem.
The technical implementation of this vulnerability stems from improper memory management practices within the SurfaceFlinger service, where a freed memory reference is subsequently accessed and written to during the setClientStateLocked operation. This use-after-free scenario creates a predictable memory corruption pattern that attackers can exploit to manipulate the execution flow of the graphics compositor service. The flaw occurs when the system attempts to update client state information while a related memory allocation has already been freed, leading to an out-of-bounds write condition that can be leveraged to execute arbitrary code with elevated privileges. This issue falls under the CWE-416 category of Use After Free, which represents a well-documented class of vulnerabilities where freed memory is accessed, potentially leading to memory corruption and privilege escalation.
The operational impact of CVE-2021-1028 extends beyond simple local privilege escalation as it represents a fundamental weakness in the Android graphics security model. Since SurfaceFlinger operates with significant system privileges and manages critical display operations, exploitation of this vulnerability could allow an attacker to gain unauthorized access to system resources, modify graphics rendering behavior, and potentially access sensitive user data or system components. The lack of user interaction requirements makes this vulnerability particularly concerning as it can be exploited automatically without requiring any form of social engineering or user deception. The vulnerability affects Android 12 systems and is identified by the Android ID A-193034683, indicating its presence in the Android security patch level for that specific version.
Mitigation strategies for this vulnerability should focus on implementing proper memory management practices within the SurfaceFlinger component and ensuring that all memory references are properly validated before use. System administrators and device manufacturers should prioritize applying the latest Android security patches that address this specific use-after-free condition. The remediation approach should include thorough code review processes to identify and eliminate similar patterns throughout the graphics subsystem and related components. Additionally, implementing memory safety mechanisms such as address space layout randomization and stack canaries can provide additional protection layers against exploitation attempts. This vulnerability aligns with ATT&CK technique T1068 which covers 'Local Privilege Escalation' and specifically addresses the use of memory corruption vulnerabilities to gain elevated system privileges. Organizations should also consider implementing runtime monitoring and anomaly detection systems to identify potential exploitation attempts targeting graphics subsystem vulnerabilities. The fix typically involves adding proper null checks and ensuring that memory references are not accessed after deallocation, which aligns with standard secure coding practices recommended by the CERT Secure Coding Standards and other industry security guidelines.