CVE-2018-20404 in EPIA-E900
Summary
by MITRE
ETK_E900.sys, a SmartETK driver for VIA Technologies EPIA-E900 system board, is vulnerable to denial of service attack via IOCTL 0x9C402048, which calls memmove and constantly fails on an arbitrary (uncontrollable) address, resulting in an eternal hang or a BSoD.
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Analysis
by VulDB Data Team • 04/24/2020
The vulnerability identified as CVE-2018-20404 affects the ETK_E900.sys driver component of VIA Technologies EPIA-E900 system boards, representing a critical denial of service weakness that can be exploited through improper input validation within the driver's IOCTL handling mechanism. This driver serves as a kernel-level interface for system board functionality and is particularly susceptible to exploitation through malicious IOCTL commands that trigger memory manipulation operations. The specific vulnerability manifests when IOCTL command 0x9C402048 is executed, which internally invokes the memmove function with an arbitrary memory address that cannot be controlled by the attacker. The flaw stems from insufficient validation of input parameters before memory operations are performed, creating a condition where the memmove function attempts to operate on invalid memory addresses, leading to system instability. This vulnerability directly maps to CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which addresses heap-based buffer overflow scenarios, both of which are common categories for kernel-mode driver vulnerabilities that can result in system crashes or hangs. The operational impact of this vulnerability extends beyond simple denial of service, as the system becomes unresponsive to legitimate input and may experience complete system lockup or blue screen of death conditions. When the memmove function encounters an invalid address during execution, it cannot properly handle the memory access violation, causing the driver to enter an infinite loop or unrecoverable state that prevents normal system operation. The attack vector is particularly concerning because it requires minimal privileges and can be triggered through standard IOCTL communication channels, making it accessible to both local and potentially remote attackers who can send malicious commands to the vulnerable driver. This vulnerability aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation', and T1499, covering 'Endpoint Denial of Service', as the system becomes unavailable to legitimate users and administrators. The flaw represents a fundamental design issue in the driver's input validation process where the system does not properly sanitize or validate memory addresses before passing them to kernel functions. The memmove operation, which is designed to copy memory regions, becomes ineffective when provided with invalid addresses, resulting in the system hanging indefinitely as the operation fails repeatedly. This creates a persistent denial of service condition that can only be resolved through system reboot or driver unloading, significantly impacting system availability and reliability. The vulnerability's severity is amplified by the fact that it operates at the kernel level, where errors can cause complete system failures rather than just application crashes, and the lack of proper error handling in the driver code prevents graceful degradation of service. System administrators and security professionals should consider this vulnerability as a high-priority issue requiring immediate attention, as it can be exploited to render systems completely inoperable and potentially create conditions that could be leveraged for more sophisticated attacks. The vulnerability demonstrates a critical gap in secure coding practices within the driver development lifecycle, particularly in the areas of input validation and error handling for kernel-mode components that directly interface with system memory management functions.