CVE-2021-34262 in STM32Cube
Summary
by MITRE • 07/23/2021
A buffer overflow vulnerability in the USBH_ParseEPDesc() function of STMicroelectronics STM32Cube Middleware v1.8.0 and below allows attackers to execute arbitrary code.
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Analysis
by VulDB Data Team • 07/27/2021
The vulnerability identified as CVE-2021-34262 represents a critical buffer overflow flaw within the USBH_ParseEPDesc() function of STMicroelectronics STM32Cube Middleware version 1.8.0 and earlier releases. This middleware component serves as a crucial interface for USB host functionality in embedded systems leveraging STMicroelectronics microcontrollers, particularly those based on the stm32f4 and stm32f7 series processors. The buffer overflow occurs during the parsing of USB endpoint descriptors, which are essential components in USB communication protocols that define the characteristics and capabilities of USB endpoints. The vulnerability stems from insufficient input validation and bounds checking within the USB host driver implementation, creating a potential entry point for malicious actors to compromise the affected systems.
The technical exploitation of this vulnerability involves crafting malicious USB endpoint descriptors that exceed the allocated buffer space within the USBH_ParseEPDesc() function. When the middleware processes these malformed descriptors, the excessive data overflows into adjacent memory regions, potentially corrupting critical system data structures or executable code. This memory corruption can lead to arbitrary code execution with the privileges of the running USB host driver process, which typically operates with elevated system privileges in embedded environments. The vulnerability is particularly concerning because USB host controllers are often integral to system boot processes and device management functions, making successful exploitation capable of compromising the entire system. According to CWE classification, this represents a classic buffer overflow vulnerability categorized under CWE-121, which specifically addresses stack-based buffer overflow conditions that can result in arbitrary code execution.
The operational impact of CVE-2021-34262 extends beyond simple code execution, as it can enable attackers to gain persistent access to embedded systems through USB interfaces. This vulnerability affects a wide range of applications including industrial control systems, automotive electronics, medical devices, and IoT deployments that utilize STMicroelectronics microcontrollers with the vulnerable middleware. The attack surface is particularly broad given that USB interfaces are commonly present in virtually all embedded systems for firmware updates, debugging, and device communication. From an ATT&CK framework perspective, this vulnerability maps to multiple techniques including T1059.007 for command and script interpreter execution and T1068 for exploit for privilege escalation, as attackers can leverage the USB host functionality to escalate their privileges within the system. The vulnerability also aligns with T1547.001 for registry run keys or startup folder, as attackers might install persistent backdoors through USB-based attacks.
Mitigation strategies for this vulnerability require immediate patching of the STM32Cube Middleware to version 1.9.0 or later, which includes proper bounds checking and input validation for USB endpoint descriptor parsing. Organizations should conduct comprehensive inventory assessments to identify all systems utilizing the vulnerable middleware versions and prioritize remediation efforts based on risk exposure. Network segmentation and USB port disablement policies can serve as temporary compensating controls to limit attack surface while permanent patches are deployed. Additionally, implementing runtime monitoring solutions capable of detecting anomalous USB behavior or memory corruption patterns can provide early warning capabilities. Security teams should also consider disabling unnecessary USB functionality on embedded systems and implementing USB device whitelisting to prevent unauthorized devices from connecting to critical systems. The vulnerability underscores the importance of secure coding practices in embedded systems and highlights the need for regular security assessments of middleware components used in critical infrastructure deployments.