An unauthenticated remote attacker can perform a command injection via Modbus-TCP or Modbus-RTU to gain read and write access on the affected device.
Unauthenticated remote attackers can exploit a command injection vulnerability in Modbus-TCP and Modbus-RTU implementations, granting them unauthorized read and write access to affected devices. This allows attackers to potentially disrupt industrial processes, steal sensitive data, or gain complete control of the compromised systems. Immediate action is required to assess and mitigate this critical vulnerability.
Step 1: Payload Delivery: The attacker crafts a malicious Modbus request, either via Modbus-TCP (over TCP port 502) or Modbus-RTU (over serial communication). This request contains a payload designed to exploit the command injection vulnerability.
Step 2: Request Transmission: The attacker sends the crafted Modbus request to the vulnerable device.
Step 3: Input Handling: The device receives the Modbus request and processes it. Due to the lack of proper input validation, the malicious payload is not detected or rejected.
Step 4: Command Injection: The device's Modbus handling logic, likely due to a programming error, directly executes the attacker-supplied command, potentially using a function like system() or exec() with unsanitized input.
Step 5: Command Execution: The attacker's injected command is executed on the device, granting the attacker unauthorized access to the system, including the ability to read and write data, and potentially execute arbitrary code.
The vulnerability stems from insufficient input validation and sanitization of user-supplied data within the Modbus protocol handling logic. Specifically, the affected device fails to properly validate Modbus function codes or register addresses, allowing an attacker to inject malicious commands disguised as legitimate Modbus requests. The device then executes these injected commands, granting the attacker unauthorized access. The root cause is likely a missing or inadequate input validation routine, combined with a flawed implementation of the command execution mechanism. This could involve a direct call to a system shell command with unsanitized parameters, leading to command injection. The lack of authentication further exacerbates the issue, enabling remote exploitation without any prior authorization.