CVE-2018-20007 in Smart AI Speaker
Summary
by MITRE
Yeelight Smart AI Speaker 3.3.10_0074 devices have improper access control over the UART interface, allowing physical attackers to obtain a root shell. The attacker can then exfiltrate the audio data, read cleartext Wi-Fi credentials in a log file, or access other sensitive device and user information.
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Analysis
by VulDB Data Team • 09/21/2023
The vulnerability CVE-2018-20007 affects Yeelight Smart AI Speaker devices running firmware version 3.3.10_0074 and exposes a critical improper access control flaw within the device's UART interface. This represents a fundamental breakdown in the device's security architecture where physical access to the hardware grants unauthorized administrative privileges. The vulnerability stems from insufficient authentication mechanisms protecting the UART communication port, which serves as a direct pathway to the device's underlying operating system. The flaw allows an attacker with physical possession of the device to bypass normal security controls and gain root shell access, fundamentally compromising the device's integrity and confidentiality.
The technical implementation of this vulnerability involves the UART interface being left accessible without proper access controls or authentication mechanisms. The Universal Asynchronous Receiver-Transmitter interface typically serves as a debugging and diagnostic port that should remain secured in production devices. However, in this case, the interface remains exposed and accessible to anyone with physical access, creating a backdoor that provides direct system-level access. This aligns with CWE-284, which addresses improper access control, and demonstrates how inadequate physical security controls can lead to complete system compromise. The root shell access enables attackers to execute arbitrary code with the highest possible privileges, rendering all other security measures ineffective.
The operational impact of this vulnerability extends far beyond simple unauthorized access, as it enables comprehensive data exfiltration and system manipulation. Attackers can exploit the compromised device to capture audio data in real-time, potentially accessing private conversations or sensitive voice commands that the device has recorded. The vulnerability also allows access to cleartext Wi-Fi credentials stored in log files, which represents a severe confidentiality breach according to the NIST SP 800-53 security controls. These credentials can be used to gain access to the attacker's home network and potentially compromise other connected devices. Additionally, the attacker gains access to other sensitive device and user information, creating a comprehensive data breach that could include personal identifiers, usage patterns, and potentially other connected IoT devices within the network ecosystem.
Mitigation strategies for CVE-2018-20007 must address both the immediate physical security concerns and the broader system vulnerabilities. Device manufacturers should implement proper access control mechanisms that disable or secure UART interfaces in production deployments, ensuring that these diagnostic ports are not accessible to unauthorized physical access. The solution should include firmware-level protections that either disable the UART interface entirely or require strong authentication before granting access. Network segmentation and monitoring should be implemented to detect unusual data flows that might indicate data exfiltration attempts. According to ATT&CK framework, this vulnerability maps to T1059.007 for command and scripting interpreter and T1071.004 for application layer protocol. Organizations should also implement regular security assessments and firmware updates to ensure that physical access controls are properly maintained. The vulnerability highlights the importance of secure by design principles and demonstrates how physical security considerations must be integrated into the overall security architecture of IoT devices to prevent such critical access control failures.