CVE-2017-10720 in Endoscope
Summary
by MITRE
Recently it was discovered as a part of the research on IoT devices in the most recent firmware for Shekar Endoscope that the desktop application used to connect to the device suffers from a stack overflow if more than 26 characters are passed to it as the Wi-Fi name. This application is installed on the device and an attacker who can provide the right payload can execute code on the user's system directly. Any breach of this system can allow an attacker to get access to all the data that the user has access too. The application uses a dynamic link library(DLL) called "avilib.dll" which is used by the application to send binary packets to the device that allow to control the device. One such action that the DLL provides is change password in the function "sendchangename" which allows a user to change the Wi-Fi name on the device. This function calls a sub function "sub_75876EA0" at address 0x758784F8. The function determines which action to execute based on the parameters sent to it. The "sendchangename" passes the datastring as the second argument which is the name we enter in the textbox and integer 1 as first argument. The rest of the 3 arguments are set to 0. The function "sub_75876EA0" at address 0x75876F19 uses the first argument received and to determine which block to jump to. Since the argument passed is 1, it jumps to 0x75876F20 and proceeds from there to address 0x75876F56 which calculates the length of the data string passed as the first parameter. This length and the first argument are then passed to the address 0x75877001 which calls the memmove function which uses a stack address as the destination where the password typed by us is passed as the source and length calculated above is passed as the number of bytes to copy which leads to a stack overflow.
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Analysis
by VulDB Data Team • 10/05/2023
CVE-2017-10720 represents a critical stack overflow vulnerability in the desktop application component of Shekar Endoscope IoT device firmware, classified under CWE-121 Stack-based Buffer Overflow. This vulnerability exists within the application's handling of Wi-Fi network names, specifically when the input exceeds 26 characters, creating a dangerous execution path that allows arbitrary code execution on the victim's system. The flaw manifests through the application's dynamic link library avilib.dll, which serves as the communication interface between the desktop software and the endoscope device. The vulnerability is particularly concerning as it operates at the kernel level through the DLL's function call chain, where the sendchangename function acts as the initial trigger point that eventually leads to the exploitable condition.
The technical exploitation pathway begins with the sendchangename function calling sub_75876EA0 at address 0x758784F8, which then evaluates the first argument value of 1 to determine the execution branch. This decision point at address 0x75876F19 routes execution to 0x75876F20, where the function calculates the length of the user-provided data string and subsequently passes this information to address 0x75877001. The critical flaw occurs when memmove function is invoked with a stack-based destination buffer, using the user-controlled input as the source and the calculated length as the byte count parameter. This direct memory copying operation without proper bounds checking creates a classic stack overflow condition that can be leveraged for privilege escalation and remote code execution.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with complete access to the user's system and all associated data. The attack vector requires minimal user interaction since the vulnerability is triggered by entering a specific string length into the Wi-Fi name field, making it particularly dangerous for IoT device users who may unknowingly expose their systems to compromise. The vulnerability aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter and T1068 for Exploitation for Privilege Escalation, as successful exploitation allows attackers to execute arbitrary commands with the privileges of the affected user. This represents a significant security risk for medical IoT devices where patient data privacy and system integrity are paramount, as the vulnerability could be exploited to access sensitive medical information or potentially manipulate the device's functionality.
Mitigation strategies should focus on input validation and bounds checking within the application's processing of user-provided strings, particularly in the avilib.dll library. Immediate patching of the firmware and desktop application components is essential to prevent exploitation, while network segmentation and access controls can limit the potential impact if exploitation occurs. The vulnerability demonstrates the critical importance of secure coding practices in IoT device development, particularly regarding buffer management and input validation. Security professionals should implement monitoring for unusual network traffic patterns and unexpected system behavior that might indicate exploitation attempts. Additionally, regular security assessments of IoT device firmware and applications are crucial to identify similar vulnerabilities in the broader IoT ecosystem, as this flaw represents a common pattern found in embedded systems where legacy code and insufficient input validation create persistent security risks. The vulnerability also highlights the need for proper software supply chain security measures, as third-party libraries like avilib.dll can introduce critical flaws that affect the entire system.