CVE-2018-3866 in SmartThings Hub STH-ETH-250
Summary
by MITRE
An exploitable buffer overflow vulnerability exists in the samsungWifiScan handler of video-core's HTTP server of Samsung SmartThings Hub STH-ETH-250 - Firmware version 0.20.17. The video-core process incorrectly extracts fields from a user-controlled JSON payload, leading to a buffer overflow on the stack. The strcpy at [8] overflows the destination buffer, which has a size of 40 bytes. An attacker can send an arbitrarily long 'callbackUrl' value in order to exploit this vulnerability.
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Analysis
by VulDB Data Team • 03/17/2020
The vulnerability identified as CVE-2018-3866 represents a critical buffer overflow flaw within the Samsung SmartThings Hub STH-ETH-250 device firmware version 0.20.17. This issue manifests in the video-core component's HTTP server implementation where the samsungWifiScan handler fails to properly validate input data from JSON payloads. The flaw resides in how the system processes user-controlled data, specifically when extracting fields from incoming requests that are destined for the video-core process. This particular implementation error creates a dangerous condition where the system does not enforce bounds checking on incoming data, allowing maliciously crafted inputs to exceed allocated memory boundaries.
The technical execution of this vulnerability occurs through a stack-based buffer overflow scenario where the system employs the strcpy function at memory location [8] to copy data into a destination buffer that is only 40 bytes in size. When an attacker provides a callbackUrl parameter exceeding this limit, the strcpy operation overflows the allocated stack space, potentially corrupting adjacent memory locations. This type of vulnerability directly maps to CWE-121 Stack-based Buffer Overflow, which is classified as a high-severity issue in the Common Weakness Enumeration catalog. The flaw demonstrates poor input validation practices and highlights the importance of implementing proper bounds checking mechanisms in network service implementations.
The operational impact of this vulnerability extends beyond simple memory corruption, as it provides attackers with a potential pathway for arbitrary code execution within the context of the video-core process. Since the SmartThings Hub serves as a central networking and automation device within home and enterprise environments, successful exploitation could allow remote attackers to gain unauthorized control over the device. This compromise could lead to complete device takeover, enabling attackers to manipulate smart home ecosystems, potentially access other networked devices, or establish persistent backdoors for further exploitation. The vulnerability affects the device's HTTP server functionality and could be exploited by attackers without requiring authentication, making it particularly dangerous in unsecured network environments.
Mitigation strategies for CVE-2018-3866 should prioritize immediate firmware updates from Samsung, as the vendor would have likely released patches addressing this specific buffer overflow condition. Network administrators should implement monitoring of HTTP traffic to the SmartThings Hub, particularly focusing on unusual callbackUrl parameter lengths that might indicate exploitation attempts. The implementation of network segmentation and access controls can help limit the potential attack surface, while disabling unnecessary HTTP services on the device can reduce exposure. Security professionals should also consider deploying intrusion detection systems that can identify anomalous JSON payload structures and monitor for patterns consistent with buffer overflow exploitation attempts. This vulnerability aligns with ATT&CK technique T1210 Exploitation of Remote Services, emphasizing the need for proper input validation and memory safety practices in network-facing applications. The flaw serves as a reminder of the critical importance of secure coding practices, particularly when handling user-supplied data in embedded systems and IoT devices where resource constraints often lead to inadequate security controls.