CVE-2015-8997 in Android
Summary
by MITRE
In TrustZone a time-of-check time-of-use race condition could potentially exist in a listener routine in all Android releases from CAF using the Linux kernel.
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Analysis
by VulDB Data Team • 12/24/2020
The vulnerability identified as CVE-2015-8997 represents a critical time-of-check time-of-use race condition within the TrustZone security framework of Android devices. This flaw exists in the listener routine component that operates within the Linux kernel environment, affecting all Android releases that utilize the Code Aurora Forum (CAF) kernel implementation. The race condition occurs when the system performs a check on a resource's state and subsequently uses that same resource before another process can modify it, creating a window of opportunity for malicious exploitation.
The technical implementation of this vulnerability stems from improper synchronization mechanisms within the TrustZone secure environment where the listener routine fails to maintain consistent state validation between the initial check and final resource utilization. This condition allows an attacker to manipulate the system's behavior by exploiting the temporal gap between when a security check is performed and when the resource is actually accessed. The vulnerability specifically impacts the secure communication pathways that rely on TrustZone's hardware-based security features, potentially enabling privilege escalation attacks.
From an operational perspective, this vulnerability poses significant risks to Android device security as it undermines the fundamental trust model that TrustZone is designed to provide. An attacker could potentially exploit this race condition to bypass security checks, gain unauthorized access to protected resources, or manipulate secure communication channels. The impact extends beyond simple privilege escalation to potentially compromise the entire secure element of the device, affecting sensitive operations such as cryptographic key handling, secure boot processes, and hardware-based authentication mechanisms. This vulnerability is particularly concerning as it affects the underlying kernel implementation rather than just application-level security.
Mitigation strategies for CVE-2015-8997 should focus on implementing proper synchronization mechanisms within the TrustZone listener routines to eliminate the race condition window. System administrators and device manufacturers should ensure that all affected Android devices receive kernel-level patches that address the specific synchronization issues in the TrustZone implementation. The remediation process should include thorough testing of the patched kernel to verify that the race condition has been eliminated without introducing regressions in system functionality. Additionally, organizations should consider implementing monitoring solutions that can detect anomalous behavior patterns that might indicate exploitation attempts. This vulnerability aligns with CWE-362, which specifically addresses race conditions, and represents a significant concern for ATT&CK technique T1068, which covers exploit for privilege escalation through kernel-level vulnerabilities. The fix typically involves modifying the kernel code to ensure atomic operations between the check and use phases, thereby preventing the temporal gap that enables exploitation.