Vulnerability Report: Stack Buffer Overflow in NETGEAR R6200V2

1. Overview

A stack-based buffer overflow vulnerability has been discovered in the httpd component of the NETGEAR R6200V2 router. This vulnerability allows remote attackers to execute arbitrary code or cause a Denial of Service (DoS) by sending a crafted request to the device.

2. Affected Product

• Device: NETGEAR R6200V2
• Firmware Version: V1.0.3.12_10.1.11
• Component: httpd binary

3. Vulnerability Details

The vulnerability is located within the keyword.cgi module of the httpd service. It is caused by unsafe handling of the bs_trustedip parameter.

Technical Analysis

When the httpd service processes a request involving keyword.cgi, it extracts the value associated with the bs_trustedip key. Due to the lack of proper boundary checks, an attacker can input an excessively long payload into this field.

The vulnerability is triggered during the following function call chain:

1. Entry: The program flow enters FUN_2dc4c.
2. Vulnerable Call: The execution proceeds to FUN_0002dba8.
3. Overflow: During the execution of FUN_0002dba8, the data supplied via bs_trustedip overwrites the stack buffer.

This overflow corrupts the return address on the stack, allowing the attacker to control the program execution flow.

4. Impact

Successful exploitation of this vulnerability can lead to critical consequences:

• Remote Code Execution (RCE): Attackers can inject and execute arbitrary shellcode with the privileges of the httpd process (typically root), leading to full system compromise.
• Denial of Service (DoS): The overflow can corrupt process memory, causing the httpd service or the entire device to crash and become unresponsive.

5. Reproduction Steps

To reproduce this vulnerability:

1. Prepare a NETGEAR R6200V2 router with firmware V1.0.3.12_10.1.11.
2. Construct an HTTP request targeting keyword.cgi.
3. Set the bs_trustedip parameter to a cyclical pattern or a long string (payload) exceeding the buffer size.
4. Send the request to the target device.
5. Observe the crash or the execution of the injected code (if a debugger is attached, the PC register will be overwritten).

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Disclaimer: This report is intended for educational and security research purposes only.