CVE-2021-27954 in ecobee3 lite
Summary
by MITRE • 08/03/2021
A heap-based buffer overflow vulnerability exists on the ecobee3 lite 4.5.81.200 device in the HKProcessConfig function of the HomeKit Wireless Access Control setup process. A threat actor can exploit this vulnerability to force the device to connect to a SSID or cause a denial of service.
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Analysis
by VulDB Data Team • 08/07/2021
The heap-based buffer overflow vulnerability identified in CVE-2021-27954 affects the ecobee3 lite smart home device running firmware version 4.5.81.200 within the HomeKit Wireless Access Control setup process. This vulnerability manifests specifically within the HKProcessConfig function, which handles configuration parameters for wireless access control mechanisms. The flaw represents a critical security weakness that undermines the device's integrity and operational reliability. The vulnerability stems from insufficient bounds checking during memory allocation and data processing within the HomeKit integration framework, creating opportunities for malicious manipulation of the device's wireless connectivity behavior.
The technical exploitation of this buffer overflow occurs when the HKProcessConfig function processes user-supplied input parameters without adequate validation or memory boundary enforcement. This allows an attacker to overflow the allocated heap memory buffer and potentially overwrite adjacent memory segments. The vulnerability falls under CWE-121 Heap-based Buffer Overflow, which is classified as a fundamental memory safety issue that enables arbitrary code execution or system instability. Attackers can leverage this weakness to inject malicious network configuration data that forces the device to connect to unauthorized wireless networks or to trigger denial of service conditions.
From an operational perspective, the impact of this vulnerability extends beyond simple device compromise to threaten broader smart home network security. When exploited, the vulnerability enables attackers to manipulate the device's wireless connectivity, potentially redirecting it to malicious access points or causing it to disconnect from legitimate networks. This capability directly conflicts with the fundamental security expectations of HomeKit devices, which are designed to maintain secure and authenticated wireless connections. The vulnerability also creates potential for persistent access points within the home network, as compromised devices can serve as entry vectors for further attacks. The denial of service aspect means that legitimate users may lose access to their smart home controls, while the forced SSID connection capability could enable man-in-the-middle attacks or network reconnaissance activities.
Security professionals should implement immediate mitigations including firmware updates from ecobee to address the identified heap overflow vulnerability. Network segmentation strategies should be employed to isolate affected devices from critical network infrastructure, while monitoring systems should be deployed to detect unauthorized wireless network changes or connection attempts. The vulnerability demonstrates the importance of secure coding practices in IoT device development, particularly regarding memory management and input validation. Organizations should also consider implementing network access controls and wireless intrusion detection systems to identify and prevent exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and persistence through network infrastructure manipulation, while the exploitation methods align with initial access and execution phases of the attack lifecycle. The vulnerability underscores the need for comprehensive security testing of IoT devices, particularly those implementing wireless access control mechanisms, and highlights the critical importance of maintaining up-to-date firmware in smart home environments.