CVE-2024-4165: Tenda G3 Buffer Overflow Vulnerability

CVE-2024-4165 Overview

A stack-based buffer overflow vulnerability has been identified in Tenda G3 router firmware version 15.11.0.17(9502). The vulnerability exists in the modifyDhcpRule function within the /goform/modifyDhcpRule endpoint. Improper handling of the bindDhcpIndex argument allows remote attackers to trigger a stack-based buffer overflow, potentially leading to arbitrary code execution or denial of service.

Critical Impact

This remotely exploitable vulnerability in the Tenda G3 router allows unauthenticated attackers to overflow the stack buffer, potentially gaining complete control over the affected device. Exploitation details have been publicly disclosed.

Affected Products

• Tenda G3 Firmware version 15.11.0.17(9502)_CN
• Tenda G3 Hardware

Discovery Timeline

• 2024-04-25 - CVE-2024-4165 published to NVD
• 2025-03-05 - Last updated in NVD database

Technical Details for CVE-2024-4165

Vulnerability Analysis

The vulnerability resides in the modifyDhcpRule function of the Tenda G3 router's web management interface. When processing HTTP requests to the /goform/modifyDhcpRule endpoint, the function fails to properly validate the length of the bindDhcpIndex parameter before copying it to a fixed-size stack buffer. This lack of boundary checking allows an attacker to supply an oversized input value that exceeds the allocated buffer space, corrupting adjacent stack memory.

The exploitation of this vulnerability can be performed remotely over the network without requiring any authentication or user interaction. An attacker who successfully exploits this flaw could overwrite critical stack data including return addresses, potentially redirecting program execution to attacker-controlled code. This could result in complete device compromise, enabling the attacker to execute arbitrary commands, modify device configuration, intercept network traffic, or render the device inoperable.

The vendor, Tenda, was contacted regarding this vulnerability but did not respond. The exploit details have been publicly disclosed, increasing the risk of exploitation in the wild.

Root Cause

The root cause is a classic CWE-121 (Stack-based Buffer Overflow) vulnerability stemming from inadequate input validation. The modifyDhcpRule function uses unsafe memory copy operations on the bindDhcpIndex parameter without first verifying that the input length fits within the destination buffer's capacity. This violates secure coding practices for handling untrusted input in embedded systems.

Attack Vector

The attack is conducted remotely over the network by sending a specially crafted HTTP POST request to the /goform/modifyDhcpRule endpoint. The attacker manipulates the bindDhcpIndex parameter with an excessively long string designed to overflow the stack buffer. No authentication is required to access this endpoint, making exploitation straightforward for any attacker with network access to the device's management interface.

The vulnerability mechanism operates as follows: when the vulnerable function processes the HTTP request, it extracts the bindDhcpIndex value and copies it into a stack-allocated buffer without length validation. By supplying a malicious payload exceeding the buffer size, an attacker can overwrite the function's return address on the stack, potentially redirecting execution to shellcode or existing executable code within the firmware.

For detailed technical analysis, refer to the GitHub IoT Vulnerability Documentation.

Detection Methods for CVE-2024-4165

Indicators of Compromise

• Unusual HTTP POST requests to /goform/modifyDhcpRule with abnormally long parameter values
• Unexpected device reboots or crashes of the Tenda G3 router
• Unauthorized configuration changes or newly added administrative accounts
• Network traffic anomalies originating from the router to unknown external destinations

Detection Strategies

• Deploy network intrusion detection signatures to identify HTTP requests to /goform/modifyDhcpRule containing oversized bindDhcpIndex values
• Monitor web server logs on the router (if accessible) for requests with unusually long query parameters
• Implement network segmentation to isolate IoT devices and monitor for lateral movement attempts
• Use application-layer firewalls to inspect and filter malicious HTTP traffic targeting known vulnerable endpoints

Monitoring Recommendations

• Enable logging on network firewalls and review access attempts to router management interfaces
• Establish baseline behavior for router management traffic and alert on deviations
• Monitor for firmware modification attempts or unexpected changes to device configuration
• Deploy honeypots mimicking vulnerable Tenda G3 devices to detect active exploitation attempts

How to Mitigate CVE-2024-4165

Immediate Actions Required

• Restrict network access to the router's web management interface using firewall rules to allow only trusted IP addresses
• Disable remote management features if not required for operational purposes
• Isolate the affected Tenda G3 router on a separate network segment with strict access controls
• Consider replacing the affected device with an alternative router from a vendor with responsive security practices

Patch Information

As of the last update, Tenda has not released a security patch for this vulnerability. The vendor was contacted about the issue but did not respond. Organizations using affected devices should implement the workarounds below until a patch becomes available or consider device replacement. Monitor VulDB #261984 and Tenda's official channels for any future security updates.

Workarounds

• Disable the web management interface entirely if not required for device administration
• Implement strict access control lists (ACLs) on upstream network devices to limit access to the /goform/modifyDhcpRule endpoint
• Deploy a web application firewall (WAF) or reverse proxy in front of the device to filter requests with oversized parameters
• Schedule regular device reboots to clear any potential compromise state while awaiting a permanent fix

# Example firewall rule to restrict management interface access (Linux iptables)
# Allow management access only from trusted admin subnet
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 80 -j DROP