CVE-2021-1027 in Android
Summary
by MITRE • 12/15/2021
In setTransactionState of SurfaceFlinger, there is possible arbitrary code execution in a privileged process due to improper casting. 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-193033243
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Analysis
by VulDB Data Team • 12/18/2021
The vulnerability identified as CVE-2021-1027 resides within the SurfaceFlinger component of Android operating systems, specifically affecting Android 12 implementations. This flaw manifests in the setTransactionState function where improper casting operations create a pathway for arbitrary code execution within a privileged process. The vulnerability represents a critical security weakness that allows for local privilege escalation without requiring any additional execution privileges or user interaction for exploitation. SurfaceFlinger serves as the core system component responsible for compositing graphics surfaces and managing display operations, making it a prime target for attackers seeking to elevate their privileges within the system.
The technical flaw stems from improper casting mechanisms within the SurfaceFlinger's transaction state management functionality. When processing transaction states, the system fails to properly validate or cast data types, creating potential for memory corruption or control flow hijacking. This improper casting vulnerability enables an attacker to manipulate the execution flow of the privileged SurfaceFlinger process, potentially allowing arbitrary code execution in a context with elevated system privileges. The flaw is particularly concerning because it operates within a system-level component that already possesses significant privileges, effectively providing attackers with a direct path to system-level compromise. The vulnerability falls under CWE-190, which addresses integer overflow and unsigned to signed conversion errors, and may also relate to CWE-121, heap-based buffer overflow conditions, depending on the specific exploitation vector.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides attackers with complete control over the device's display and graphics processing capabilities. An attacker with local access could leverage this vulnerability to execute malicious code with the same privileges as the SurfaceFlinger service, potentially enabling full system compromise, data exfiltration, or persistent backdoor installation. The lack of user interaction requirements makes this vulnerability particularly dangerous as it can be exploited automatically without any user awareness or consent. This type of vulnerability directly aligns with ATT&CK technique T1068, which covers 'Local Privilege Escalation', and T1547.001, covering 'Registry Run Keys / Startup Folder', as the elevated privileges could enable persistence mechanisms within the system. The exploitation of this vulnerability could also enable further attacks on other system components, as the compromised SurfaceFlinger process has access to graphics-related system resources and potentially sensitive data.
Mitigation strategies for CVE-2021-1027 should focus on immediate patch deployment for Android 12 systems and potentially older versions that may be affected. Organizations should implement comprehensive monitoring for suspicious system behavior, particularly around graphics processing and display management functions. The Android security team has addressed this vulnerability in subsequent updates, and system administrators should ensure all devices are updated to the latest security patches. Additionally, implementing runtime monitoring and anomaly detection for unauthorized code execution within privileged system processes can help detect exploitation attempts. Network segmentation and least privilege principles should be maintained to limit potential damage if exploitation occurs, though the vulnerability's nature suggests that successful exploitation would likely provide complete system compromise. The vulnerability highlights the importance of secure coding practices and proper input validation, particularly within system-level components that handle sensitive operations.