CVE-2021-0697 in Android
Summary
by MITRE • 09/14/2022
In PVRSRVRGXSubmitTransferKM of rgxtransfer.c, there is a possible user after free 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-238918403
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Analysis
by VulDB Data Team • 10/17/2022
The vulnerability identified as CVE-2021-0697 represents a critical security flaw within the Android graphics subsystem, specifically affecting the PowerVR Services driver component. This issue manifests in the PVRSRVRGXSubmitTransferKM function located in the rgxtransfer.c source file, where a race condition enables a user-after-free scenario that can be exploited for privilege escalation. The vulnerability affects Android SoC implementations and has been assigned Android ID A-238918403, indicating its significance within the Android security framework. The flaw exists at the kernel level within the graphics processing unit driver, making it particularly dangerous as it operates in a privileged execution context.
The technical implementation of this vulnerability stems from improper synchronization mechanisms within the graphics driver's memory management system. When the PVRSRVRGXSubmitTransferKM function processes graphics transfer operations, it fails to adequately protect shared resources from concurrent access patterns. The race condition occurs during the lifecycle management of graphics buffer objects where a freed memory region may still be referenced by subsequent operations before the memory is properly deallocated. This creates a window where an attacker can manipulate the system into executing arbitrary code with elevated privileges, effectively bypassing normal access controls and user permissions. The vulnerability operates under CWE-362, which specifically addresses race conditions in concurrent programming environments, making it a classic example of improper synchronization leading to memory safety issues.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with complete control over the graphics processing unit and potentially the underlying system. An attacker with local access can exploit this flaw to gain kernel-level privileges without requiring additional execution capabilities or user interaction for exploitation. This means that any application running with standard user permissions could theoretically leverage this vulnerability to execute malicious code with system-level privileges, potentially leading to complete system compromise. The attack surface includes all Android devices utilizing affected PowerVR graphics drivers, making it particularly widespread across various device manufacturers and model lines. The lack of user interaction requirements significantly increases the exploitability factor, as the vulnerability can be triggered automatically without requiring user deception or specific actions.
Mitigation strategies for CVE-2021-0697 should focus on immediate patch deployment and system hardening measures. Device manufacturers must prioritize rolling out security updates that address the race condition in the graphics driver's memory management functions. The fix typically involves implementing proper synchronization primitives such as mutex locks or atomic operations to prevent concurrent access to shared resources during buffer deallocation. System administrators should also consider implementing additional security controls including kernel address space layout randomization, stack canaries, and code integrity checks to reduce the effectiveness of potential exploitation attempts. Organizations should monitor for related vulnerabilities in the PowerVR driver ecosystem and ensure comprehensive testing of security patches before deployment. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, specifically targeting kernel-level access and memory corruption methods that leverage race conditions to achieve unauthorized system control.