CVE-2018-3875 in SmartThings Hub STH-ETH-250
Summary
by MITRE
An exploitable buffer overflow vulnerability exists in the credentials 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 strncpy overflows the destination buffer, which has a size of 2,000 bytes. An attacker can send an arbitrarily long "sessionToken" value in order to exploit this vulnerability.
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Analysis
by VulDB Data Team • 05/08/2023
The vulnerability described in CVE-2018-3875 represents a critical buffer overflow flaw within the video-core HTTP server component of Samsung SmartThings Hub STH-ETH-250 firmware version 0.20.17. This issue resides in the credentials handling mechanism where the system processes user-controlled JSON payloads without proper input validation. The flaw manifests when the video-core process attempts to extract fields from incoming JSON data, specifically targeting the sessionToken parameter. The vulnerability is classified as a stack-based buffer overflow according to CWE-121, which occurs when a program writes data to a buffer located on the stack without checking the buffer boundaries. The destination buffer has a fixed size of 2,000 bytes, but the strncpy function does not properly validate the source data length, allowing attackers to overflow this allocated space. This type of vulnerability falls under the ATT&CK technique T1203 - Exploitation for Client Execution, as it enables remote code execution through malformed input processing. The root cause stems from improper bounds checking in string manipulation operations, where the system assumes that input data will not exceed predetermined limits. The specific exploitation vector involves sending an arbitrarily long sessionToken value in the JSON payload, which directly leads to stack corruption and potential privilege escalation. The vulnerability impacts the device's authentication and authorization mechanisms, potentially allowing unauthorized access to the SmartThings Hub's network services and administrative functions.
The operational impact of this buffer overflow vulnerability extends beyond simple denial of service scenarios to encompass full system compromise capabilities. When exploited successfully, the vulnerability can lead to arbitrary code execution on the affected SmartThings Hub, enabling attackers to gain persistent access to the device and its network. The stack-based nature of the overflow means that attackers can overwrite return addresses and function pointers, potentially redirecting program execution flow to malicious code. This vulnerability is particularly concerning for IoT devices like the SmartThings Hub, as it represents a pathway for attackers to establish persistent footholds within home networks and potentially escalate privileges to administrative levels. The exploitation requires minimal network access and can be performed remotely, making it an attractive target for threat actors seeking to compromise smart home ecosystems. The vulnerability's presence in firmware version 0.20.17 indicates that it was likely present in multiple iterations of the SmartThings Hub's software stack, affecting a significant number of deployed devices. The impact on network security is substantial, as the compromised hub could serve as a pivot point for attacking other connected devices within the same network segment, potentially leading to broader security breaches.
Mitigation strategies for CVE-2018-3875 must address both immediate remediation and long-term security posture improvements. The primary recommendation involves updating the firmware to a version that contains proper bounds checking and input validation for JSON payload processing. Samsung should provide security patches that implement proper buffer size validation before string operations occur, specifically addressing the strncpy function's behavior with user-controlled data. Network segmentation and access control measures should be implemented to limit exposure of the SmartThings Hub to untrusted networks. The implementation of input sanitization routines that validate data length before processing can prevent similar vulnerabilities from occurring in the future. Security monitoring should include detection of anomalous JSON payload sizes, particularly those exceeding normal sessionToken length parameters. Organizations should also implement network-based intrusion detection systems that can identify and block malicious JSON payloads attempting to exploit this vulnerability. The vulnerability demonstrates the importance of secure coding practices, particularly around buffer management and input validation, which aligns with CWE-665 and the broader principles of secure software development lifecycle implementation. Regular firmware updates and vulnerability assessments should be conducted to ensure that similar issues are not present in other components of the SmartThings ecosystem, as the vulnerability represents a pattern that could affect other services within the device's HTTP server implementation.