CVE-2021-20173

Step 1: Trigger Update Check: The attacker sends a crafted SOAP request to the router's SOAP interface, simulating a firmware update check. This request contains malicious payloads embedded within preconfigured values used by the update process.

Step 2: Payload Injection: The crafted SOAP request includes malicious commands disguised as legitimate update parameters. These commands are designed to execute arbitrary code on the router.

Step 3: Command Execution: The router's update functionality processes the SOAP request. Due to the lack of input validation, the malicious commands embedded in the preconfigured values are executed by the system with elevated privileges.

Step 4: System Compromise: The executed commands allow the attacker to gain control of the router, potentially leading to data exfiltration, network pivoting, and further compromise of connected devices.

The vulnerability stems from insufficient input validation within the firmware update functionality of the Netgear Nighthawk R6700. Specifically, the device's SOAP interface, used for checking for firmware updates, fails to properly sanitize user-supplied input before passing it to a system command. The flaw lies in how the router handles preconfigured values during the update check process. An attacker can inject malicious commands into these values, which are then executed with elevated privileges. The root cause is a lack of proper input validation and sanitization of parameters used in the update process. The SOAP interface likely constructs a command string using user-controlled data without adequate filtering or escaping, leading to command injection.