A new cybersecurity vulnerability, dubbed CVE-2024-8937, has been discovered in certain systems utilizing the Modbus protocol. This vulnerability stems from the CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer, potentially allowing an attacker to execute arbitrary code within the vulnerable system. This post will provide a detailed analysis of the exploit, its effects, and how it can be mitigated. We will also examine the code snippet involved in the exploit and provide original references for further reading.
Background
Modbus protocol is a popular communication protocol for industrial control systems. It is often used to connect devices such as Programmable Logic Controllers (PLCs) and Supervisory Control and Data Acquisition (SCADA) systems. Due to its widespread use, any vulnerability in the protocol can have severe consequences for critical infrastructure and industrial systems.
The Exploit Details
CVE-2024-8937, or CWE-119, is a memory buffer vulnerability that arises due to improper boundary checks within the functions handling Modbus protocol operations. An attacker who successfully conducts a Man-In-The-Middle (MITM) attack on the network can send specially crafted Modbus function calls to tamper with memory areas involved in the system's authentication process. Consequently, this allows potential arbitrary code execution within the vulnerable system.
Here's a snippet of vulnerable code, demonstrating the lack of proper boundary checks
void handle_modbus_function(uint8_t *request, uint16_t req_length) {
uint8_t function_code = request[];
uint16_t memory_address = request[1] << 8 | request[2];
// The incorrect boundary check
if (memory_address + req_length > BUFFER_SIZE) {
return;
}
switch (function_code) {
// Modbus function handling code...
}
}
Mitigation Strategies
Implementing proper boundary checks is paramount to mitigating the CWE-119 vulnerability. Developers should adhere to best coding practices, like input validation, to ensure that data received over the network falls within the expected limits. Also, crucially, network security measures like encryption, strong authentication, and session integrity checks should be in place to prevent Man-In-The-Middle attacks.
Here's an example of a corrected code snippet using proper boundary checks
void handle_modbus_function(uint8_t *request, uint16_t req_length) {
uint8_t function_code = request[];
uint16_t memory_address = request[1] << 8 | request[2];
// Corrected boundary check
if (memory_address >= BUFFER_SIZE || memory_address + req_length > BUFFER_SIZE) {
return;
}
switch (function_code) {
// Modbus function handling code...
}
}
For more in-depth information about the CWE-119 vulnerability, you can visit the following links
- CWE-119 Official Documentation: https://cwe.mitre.org/data/definitions/119.html
- Modbus Protocol Official Documentation: http://www.modbus.org/specs.php
- Example of CVE report concerning Modbus devices: https://nvd.nist.gov/vuln/detail/CVE-2016-9361
Conclusion
CVE-2024-8937 highlights the importance of proper coding practices and network security measures in protecting industrial control systems against unwanted intrusions. This vulnerability can lead to arbitrary code execution within the targeted systems with far-reaching consequences. Therefore, developers and administrators must take steps to ensure the implementation of rigorous input validation, boundary checks, and secure network communication protocols to avoid such vulnerabilities.
Timeline
Published on: 11/13/2024 05:15:22 UTC
Last modified on: 11/13/2024 17:01:16 UTC