CVE-2016-8440 in Android
Summary
by MITRE
Possible buffer overflow in SMMU system call. Improper input validation in ADSP SID2CB system call may result in hypervisor memory overwrite. Product: Android. Versions: Kernel 3.18. Android ID: A-31625306. References: QC-CR#1036747.
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Analysis
by VulDB Data Team • 01/04/2017
The vulnerability identified as CVE-2016-8440 represents a critical buffer overflow condition within the System Memory Management Unit (SMMU) subsystem of Android devices running kernel version 3.18. This flaw manifests in the ADSP SID2CB system call, which operates within the hypervisor context and handles memory management operations for audio digital signal processing components. The vulnerability stems from inadequate input validation mechanisms that fail to properly sanitize or verify the size and content of data structures passed to the system call. When malicious or malformed input is processed through this interface, the insufficient boundary checking allows an attacker to write beyond allocated memory boundaries, potentially corrupting adjacent memory regions within the hypervisor's address space.
The technical implementation of this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow scenarios. The flaw operates at a privilege level that is particularly concerning since it involves the hypervisor layer, making it susceptible to exploitation by malicious applications or system components that can trigger the vulnerable system call. The ADSP SID2CB interface specifically handles the translation of system identifiers to control blocks, and the lack of proper input validation in this pathway creates a direct avenue for memory corruption. This type of vulnerability falls under the ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation' and T1059, covering 'Command and Scripting Interpreter', as exploitation would likely require crafting specific inputs to trigger the buffer overflow condition.
The operational impact of this vulnerability extends beyond simple memory corruption, as successful exploitation could result in complete system compromise through hypervisor privilege escalation. The hypervisor serves as a critical isolation layer between the operating system and hardware resources, making any vulnerability within this context potentially catastrophic. An attacker who successfully exploits this buffer overflow could gain the ability to execute arbitrary code within the hypervisor context, potentially leading to full system takeover, persistent rootkit installation, or complete bypass of Android security mechanisms. The vulnerability is particularly dangerous because it can be triggered through legitimate system calls, meaning that exploitation does not require elevated privileges or special attack vectors, and could potentially be exploited by malicious applications already running on the device.
Mitigation strategies for this vulnerability should focus on immediate kernel updates and patches that implement proper input validation and boundary checking within the ADSP SID2CB system call interface. The recommended approach involves adding explicit size validation checks and implementing stack canaries or similar memory protection mechanisms to detect buffer overflow conditions before they can cause memory corruption. Additionally, Android security teams should consider implementing runtime memory protection features such as address space layout randomization and data execution prevention to make exploitation more difficult. The patch implementation should also include enhanced logging and monitoring capabilities to detect potential exploitation attempts, while system administrators should ensure that all devices running kernel 3.18 or earlier versions are updated to patched versions that address the specific buffer overflow condition in the SMMU subsystem. Organizations should also implement network monitoring to detect anomalous system call patterns that might indicate exploitation attempts targeting this specific vulnerability.