CVE-2021-3432 in zephyrproject-rtos
Summary
by MITRE • 06/29/2022
Invalid interval in CONNECT_IND leads to Division by Zero. Zephyr versions >= v1.14.0 Divide By Zero (CWE-369). For more information, see https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-7364-p4wc-8mj4
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Analysis
by VulDB Data Team • 07/16/2022
The vulnerability identified as CVE-2021-3432 represents a critical division by zero error within the Zephyr real-time operating system that occurs during Bluetooth Low Energy connection handling. This flaw specifically manifests when processing CONNECT_IND packets, which are fundamental components of the Bluetooth connection establishment process. The vulnerability affects Zephyr versions 1.14.0 and later, making it a persistent issue across multiple release branches of this widely-used embedded operating system. The root cause stems from an invalid interval value being processed during the connection indication phase, which subsequently triggers a mathematical division operation by zero, leading to system instability and potential denial of service conditions.
The technical implementation of this vulnerability resides in the Bluetooth stack's handling of connection parameters where the system fails to properly validate the interval field within CONNECT_IND packets before performing arithmetic operations. When an attacker crafts a malicious CONNECT_IND packet with an invalid interval value that results in a zero denominator during calculation, the operating system's Bluetooth subsystem encounters a division by zero exception. This condition violates the fundamental principles of arithmetic operations and causes the kernel to either crash or enter an undefined state. The vulnerability operates at the kernel level within the Bluetooth protocol stack, making it particularly dangerous as it can affect the entire system's ability to maintain or establish Bluetooth connections.
From an operational perspective, this vulnerability presents significant risks to embedded systems that rely on Zephyr for Bluetooth connectivity, particularly in IoT devices, wearables, and industrial control systems where continuous connectivity is critical. The division by zero condition can lead to complete system crashes, requiring manual intervention or device reboot to restore functionality. Attackers could potentially exploit this vulnerability to perform denial of service attacks against connected devices, disrupting communication channels and potentially compromising the security posture of larger network ecosystems. The impact extends beyond individual device compromise to affect entire connected infrastructures where multiple devices rely on stable Bluetooth connections for their operations.
Mitigation strategies for CVE-2021-3432 should prioritize immediate patching of affected Zephyr versions through the official security advisories provided by the Zephyr project maintainers. Organizations should implement comprehensive monitoring of Bluetooth connection states to detect anomalous behavior that might indicate exploitation attempts. Network segmentation and access controls should be strengthened to limit exposure of vulnerable devices to untrusted networks. Additionally, implementing proper input validation mechanisms within application layers that interact with Bluetooth functionality can provide additional defense-in-depth measures. The vulnerability aligns with CWE-369, which specifically addresses division by zero conditions in software systems, and can be mapped to ATT&CK technique T1499.004 for network disruption attacks, emphasizing the importance of proper error handling and input validation in embedded systems security architectures.