CVE-2023-2234 in zephyr
Summary
by MITRE • 07/10/2023
Union variant confusion allows any malicious BT controller to execute arbitrary code on the Zephyr host.
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Analysis
by VulDB Data Team • 07/27/2023
The vulnerability identified as CVE-2023-2234 represents a critical security flaw in the Zephyr operating system's Bluetooth implementation that stems from improper handling of union data structures during Bluetooth controller operations. This issue specifically affects the Bluetooth stack implementation within Zephyr, where developers have failed to properly validate or sanitize data when processing union variants that are used to manage different Bluetooth protocol layers. The flaw creates a dangerous condition where a malicious Bluetooth controller can manipulate the union structure to overwrite critical memory locations, effectively allowing remote code execution on the host system. Such a vulnerability is particularly concerning given the widespread use of Zephyr in embedded IoT devices, automotive systems, and industrial control environments where Bluetooth connectivity is prevalent.
The technical root cause of this vulnerability lies in the improper management of union data types within the Bluetooth protocol stack implementation. In C and C++ programming languages, unions are memory structures that can hold different data types at the same memory location, with only one member being active at any given time. When the Bluetooth controller communicates with the host system through the Zephyr stack, it passes data structures that include union variants to represent different Bluetooth protocol elements. The flaw occurs when the host system fails to properly validate the data type being passed through these union structures, allowing a malicious controller to craft specific data sequences that cause the union to be interpreted as a different data type than intended. This misinterpretation leads to memory corruption that can be exploited to redirect program execution flow and ultimately achieve arbitrary code execution on the host system.
The operational impact of CVE-2023-2234 extends far beyond simple privilege escalation, as it represents a complete compromise of the host system's security posture. An attacker with physical proximity to a vulnerable device can exploit this vulnerability without requiring any authentication or network access, making it particularly dangerous in environments where Bluetooth devices are frequently paired with other systems. The vulnerability affects the fundamental communication layer between the Bluetooth controller and host, meaning that any device running Zephyr with Bluetooth capabilities could be compromised. This includes smart home devices, industrial sensors, automotive systems, and medical devices that rely on Zephyr's Bluetooth stack for connectivity. The attack surface is further expanded because the vulnerability exists at the protocol implementation level rather than at the application layer, making it extremely difficult to detect or prevent through traditional application-level security measures.
From a cybersecurity perspective, this vulnerability aligns with several ATT&CK framework techniques including T1059.007 for command and script interpreter and T1547.001 for registry run keys. The vulnerability also maps to CWE-121, which describes stack-based buffer overflow conditions, and CWE-125, which covers out-of-bounds read scenarios. Organizations using Zephyr-based systems should immediately implement mitigations including firmware updates from the Zephyr project maintainers, network segmentation to limit Bluetooth exposure, and monitoring for unusual Bluetooth pairing or connection patterns. Additionally, implementing proper input validation and bounds checking in union-based data structures should become standard practice for all Bluetooth protocol implementations. The vulnerability underscores the critical importance of proper memory management in embedded systems and demonstrates how seemingly minor implementation flaws can lead to complete system compromise. Given the prevalence of Zephyr in IoT deployments, this vulnerability represents a significant risk that requires immediate attention from device manufacturers and system administrators across multiple industries.