CVE-2022-39344 in USBX
Summary
by MITRE • 11/05/2022
Azure RTOS USBX is a USB host, device, and on-the-go (OTG) embedded stack, that is fully integrated with Azure RTOS ThreadX. Prior to version 6.1.12, the USB DFU UPLOAD functionality may be utilized to introduce a buffer overflow resulting in overwrite of memory contents. In particular cases this may allow an attacker to bypass security features or execute arbitrary code. The implementation of `ux_device_class_dfu_control_request` function prevents buffer overflow during handling of DFU UPLOAD command when current state is `UX_SYSTEM_DFU_STATE_DFU_IDLE`. This issue has been patched, please upgrade to version 6.1.12. As a workaround, add the `UPLOAD_LENGTH` check in all possible states.
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Analysis
by VulDB Data Team • 12/04/2022
The vulnerability identified as CVE-2022-39344 affects Azure RTOS USBX, an embedded USB stack that integrates with Azure RTOS ThreadX and supports USB host, device, and on-the-go functionality. This embedded system component is widely used in IoT devices, industrial control systems, and embedded applications where USB connectivity is required. The flaw resides in the USB Device Firmware Update (DFU) implementation within the USBX stack, specifically in how it processes control requests during the DFU UPLOAD operation. The vulnerability represents a classic buffer overflow condition that occurs when handling USB DFU commands, potentially allowing attackers to manipulate memory contents and compromise system security.
The technical implementation flaw occurs within the `ux_device_class_dfu_control_request` function, which fails to properly validate buffer boundaries when processing DFU UPLOAD requests in states other than `UX_SYSTEM_DFU_STATE_DFU_IDLE`. This function handles USB control requests for DFU operations, and when the device is in certain operational states, it does not adequately check the length parameter provided in the UPLOAD command. The missing validation allows an attacker to craft malicious USB traffic that can cause memory corruption by writing beyond allocated buffer boundaries. This type of vulnerability maps directly to CWE-121, which describes stack-based buffer overflow conditions, and CWE-787, which covers out-of-bounds write vulnerabilities. The vulnerability can be exploited through USB physical access or via network-connected USB devices that can be manipulated to send crafted commands.
The operational impact of this vulnerability extends beyond simple memory corruption, as it can enable attackers to bypass security mechanisms and execute arbitrary code on affected devices. When an attacker successfully exploits this buffer overflow, they can overwrite critical memory locations including return addresses, function pointers, or security-related variables that control device behavior. This capability allows for privilege escalation, persistent backdoor installation, or complete system compromise, particularly in embedded environments where devices may operate with elevated privileges or critical system functions. The vulnerability affects devices running Azure RTOS versions prior to 6.1.12, making it particularly concerning for organizations with large deployments of IoT devices, industrial equipment, or embedded systems that may not receive regular security updates. The threat landscape for such vulnerabilities aligns with ATT&CK technique T1059.007, which covers command and scripting interpreter execution, and T1068, which addresses exploit for privilege escalation.
Organizations should immediately upgrade to Azure RTOS USBX version 6.1.12 to remediate this vulnerability, as this release includes the necessary patches to prevent the buffer overflow condition. The patch specifically addresses the missing validation in the `ux_device_class_dfu_control_request` function by implementing proper bounds checking for the UPLOAD_LENGTH parameter across all device states. As a temporary mitigation, administrators can implement a workaround by adding explicit UPLOAD_LENGTH checks in all possible device states, though this approach requires careful code modification and testing to ensure compatibility with existing applications. Security teams should conduct comprehensive vulnerability assessments of their embedded device fleets, particularly focusing on USB-connected systems and IoT deployments that may be running vulnerable versions of Azure RTOS. The vulnerability highlights the importance of secure coding practices in embedded systems and demonstrates how seemingly minor implementation flaws in device drivers can have significant security implications, particularly in resource-constrained environments where traditional security controls may be limited.