CVE-2021-3434 in zephyrproject-rtos
Summary
by MITRE • 06/29/2022
Stack based buffer overflow in le_ecred_conn_req(). Zephyr versions >= v2.5.0 Stack-based Buffer Overflow (CWE-121). For more information, see https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-8w87-6rfp-cfrm
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Analysis
by VulDB Data Team • 07/16/2022
The vulnerability identified as CVE-2021-3434 represents a critical stack-based buffer overflow in the Zephyr real-time operating system affecting versions 2.5.0 and later. This flaw exists within the le_ecred_conn_req() function, which handles Bluetooth Low Energy connection requests in the Zephyr Bluetooth subsystem. The vulnerability stems from inadequate input validation and buffer size management during the processing of connection parameters, creating a scenario where maliciously crafted data can overwrite adjacent stack memory locations. The issue falls under CWE-121, which specifically addresses stack-based buffer overflow conditions where insufficient bounds checking allows attackers to write beyond the allocated buffer boundaries.
The technical implementation of this vulnerability occurs when the le_ecred_conn_req() function processes incoming Bluetooth connection requests without properly validating the length of incoming data structures. When a remote attacker sends specially crafted connection parameters, the function fails to verify that the data fits within the pre-allocated stack buffer, enabling arbitrary memory overwrite conditions. This flaw can be exploited through the Bluetooth protocol stack, requiring minimal privileges to trigger since the vulnerability exists within the system's network processing components. The attack vector is particularly concerning as it operates at the protocol level, potentially allowing remote code execution or system compromise when the overflow corrupts critical stack metadata such as return addresses or function pointers.
The operational impact of this vulnerability extends beyond simple memory corruption, as it creates opportunities for privilege escalation and persistent system compromise within embedded environments that rely on Zephyr for Bluetooth connectivity. Systems utilizing affected Zephyr versions may experience unexpected crashes, data corruption, or complete system instability when processing malformed connection requests. The vulnerability affects a broad range of embedded devices including IoT sensors, wearables, medical devices, and industrial control systems that depend on Zephyr's Bluetooth stack for connectivity. From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1059.007 for command and control through Bluetooth protocols, and T1566 for initial access via wireless network protocols, making it particularly dangerous in environments where physical proximity or network access is achievable.
Mitigation strategies for CVE-2021-3434 require immediate patching of affected Zephyr installations to version 2.5.1 or later, which contains the necessary buffer validation fixes. Organizations should implement network segmentation and Bluetooth access controls to limit exposure, while also conducting thorough vulnerability assessments of all embedded systems running affected Zephyr versions. The fix typically involves implementing proper input length validation and bounds checking within the le_ecred_conn_req() function, ensuring that all incoming data structures are verified against expected buffer sizes before processing. Additionally, system administrators should monitor for anomalous Bluetooth connection patterns that might indicate exploitation attempts, and maintain up-to-date security monitoring solutions capable of detecting protocol-level anomalies in embedded network traffic. The vulnerability demonstrates the importance of secure coding practices in embedded systems development, particularly regarding memory management and input validation in real-time operating system components that handle network communications.