CVE-2019-9470 in Android
Summary
by MITRE
In dma_sblk_start of abc-pcie.c, there is a possible out of bounds write due to a missing bounds check. This could lead to local escalation of privilege with System execution privileges needed. User interaction is not needed for exploitation. Product: Android Versions: Android kernel Android ID: A-144167528
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Analysis
by VulDB Data Team • 01/07/2020
The vulnerability identified as CVE-2019-9470 represents a critical out-of-bounds write flaw within the Android kernel's pcie driver implementation. This issue exists in the dma_sblk_start function located in the abc-pcie.c source file, where inadequate bounds checking allows for memory corruption that can be exploited for privilege escalation. The vulnerability specifically affects Android kernel implementations and was tracked under Android ID A-144167528, highlighting its significance within the mobile operating system ecosystem. The flaw manifests as a potential system-level security breach that could enable malicious actors to elevate their privileges from standard user level to system level execution privileges.
The technical nature of this vulnerability stems from the absence of proper input validation within the dma_sblk_start function, which processes data block starting operations for PCIe (Peripheral Component Interconnect Express) communication channels. When the driver handles memory allocation or data transfer operations, it fails to verify that array indices or buffer boundaries remain within acceptable limits. This missing bounds check creates a condition where malicious input or crafted parameters can cause the system to write data beyond the intended memory allocation, potentially overwriting critical system structures or executable code. The vulnerability falls under CWE-129, which specifically addresses insufficient bounds checking, and represents a classic example of memory safety issues that can lead to arbitrary code execution. The flaw operates at the kernel level where it can directly manipulate system memory structures and process execution contexts.
The operational impact of CVE-2019-9470 extends beyond simple data corruption, as it enables local privilege escalation without requiring user interaction or elevated privileges to initiate the attack. This means that any malicious application running with standard user privileges could potentially exploit this vulnerability to gain system-level access, effectively bypassing Android's security model and access controls. The attack vector operates entirely within the kernel space, making it particularly dangerous as it can compromise the integrity of the entire operating system. The vulnerability's exploitation requires only system execution privileges, indicating that the attack can be launched through normal system processes rather than requiring special administrative access. This characteristic aligns with ATT&CK technique T1068, which covers local privilege escalation through kernel exploits, and demonstrates how kernel-level vulnerabilities can be leveraged to achieve complete system compromise.
Mitigation strategies for this vulnerability should focus on implementing proper bounds checking mechanisms within the affected driver code, specifically within the dma_sblk_start function. The recommended approach involves adding comprehensive input validation to ensure that all array indices, buffer sizes, and memory access operations remain within predefined limits before any data manipulation occurs. System administrators and device manufacturers should prioritize applying kernel patches that address this specific bounds checking deficiency, as the vulnerability can be exploited to gain complete system control. Additionally, implementing kernel address space layout randomization and other exploit mitigation techniques can help reduce the effectiveness of potential exploitation attempts. Organizations should also conduct thorough security assessments of their Android kernel implementations to identify similar vulnerabilities in other driver components, as this type of memory corruption flaw can exist in multiple locations within kernel codebases. The vulnerability underscores the importance of rigorous code review processes and automated security testing for kernel-level components, particularly those handling hardware communication protocols such as PCIe interfaces.