CVE-2016-8439 in Android
Summary
by MITRE
Possible buffer overflow in trust zone access control API. Buffer overflow may occur due to lack of buffer size checking. Product: Android. Versions: Kernel 3.18. Android ID: A-31625204. References: QC-CR#1027804.
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Analysis
by VulDB Data Team • 01/04/2017
The vulnerability identified as CVE-2016-8439 represents a critical buffer overflow condition within the TrustZone access control API of Android kernel versions, specifically affecting kernel version 3.18. This flaw resides in the secure element handling mechanisms that govern how trusted applications interact with the hardware security modules. The vulnerability stems from inadequate input validation and buffer size checking within the kernel-level implementation of TrustZone interfaces, creating a potential pathway for malicious code execution in the secure world. The Android ID A-31625204 and reference QC-CR#1027804 indicate this issue was tracked through Qualcomm's internal vulnerability management systems, highlighting its significance in mobile security architecture.
The technical implementation of this vulnerability occurs when the kernel processes API calls from trusted applications that attempt to access TrustZone resources. Without proper bounds checking on buffer sizes, malicious inputs can overwrite adjacent memory locations within the secure kernel space. This buffer overflow condition allows attackers to potentially corrupt critical data structures, overwrite function pointers, or execute arbitrary code within the secure execution environment. The flaw specifically manifests in the TrustZone access control API where data is passed between the normal world and the secure world of the processor, creating a potential attack surface that could compromise the fundamental security guarantees provided by the TrustZone architecture.
The operational impact of CVE-2016-8439 extends beyond simple memory corruption, as it fundamentally undermines the security model of Android devices that rely on TrustZone for hardware-level security. Attackers who successfully exploit this vulnerability could gain unauthorized access to secure storage, compromise cryptographic keys, or escalate privileges from the normal world to the secure world. This represents a severe threat to device integrity and user data confidentiality, as the secure element that should protect sensitive operations becomes vulnerable to exploitation. The vulnerability affects all Android devices running kernel 3.18 or earlier versions, potentially impacting millions of mobile devices globally, and creates a persistent risk for data breaches and privilege escalation attacks.
Mitigation strategies for CVE-2016-8439 require immediate patching of affected kernel versions through Android security updates, with particular emphasis on implementing proper buffer size validation and bounds checking within the TrustZone access control API. Organizations should prioritize updating their Android devices to kernel versions that include the patched TrustZone implementation, as well as implementing runtime monitoring to detect potential exploitation attempts. Security teams should also consider implementing additional defensive measures such as code integrity checking, memory protection mechanisms, and regular security audits of kernel modules. This vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and represents a significant concern for ATT&CK technique T1068, which involves exploiting legitimate credentials and privileges to gain system access. The patching process should be comprehensive, covering not only the immediate kernel vulnerability but also ensuring proper validation of all TrustZone API interfaces and maintaining up-to-date security configurations across all affected Android devices.