CVE-2026-5036: Tenda 4G06 Buffer Overflow Vulnerability

CVE-2026-5036 Overview

A stack-based buffer overflow vulnerability has been identified in Tenda 4G06 routers running firmware version 04.06.01.29. This vulnerability exists in the fromDhcpListClient function within the /goform/DhcpListClient endpoint. By manipulating the page argument, an authenticated remote attacker can trigger a stack-based buffer overflow condition, potentially leading to arbitrary code execution or denial of service on the affected device.

Critical Impact

This network-accessible vulnerability in consumer router firmware could allow attackers to compromise network infrastructure, intercept traffic, or use the device as a pivot point for further attacks within the network.

Affected Products

• Tenda 4G06 Hardware version 3.0
• Tenda 4G06 Firmware version 04.06.01.29
• Tenda 4G06 devices with vulnerable DHCP client list endpoint

Discovery Timeline

• 2026-03-29 - CVE-2026-5036 published to NVD
• 2026-03-30 - Last updated in NVD database

Technical Details for CVE-2026-5036

Vulnerability Analysis

The vulnerability resides in the fromDhcpListClient function, which handles requests to the /goform/DhcpListClient endpoint on the Tenda 4G06 router's web management interface. This function processes the page parameter without adequate bounds checking, resulting in a classic stack-based buffer overflow condition (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer).

When a malicious request containing an oversized or specially crafted page argument is submitted to the vulnerable endpoint, the function writes data beyond the allocated stack buffer. This memory corruption can overwrite critical stack elements including the return address, potentially allowing an attacker to redirect execution flow to attacker-controlled code.

The exploit for this vulnerability has been made public, increasing the risk of exploitation in the wild. Given the nature of IoT devices like routers, which often lack robust security monitoring, successful exploitation could go undetected while providing attackers with persistent network access.

Root Cause

The root cause of CVE-2026-5036 is insufficient input validation and boundary checking in the fromDhcpListClient function. The page parameter is accepted from user input and copied into a fixed-size stack buffer without verifying that the input length does not exceed the buffer capacity. This failure to implement proper bounds checking allows an attacker to overflow the buffer and corrupt adjacent memory on the stack.

Attack Vector

The attack can be initiated remotely over the network against the router's web management interface. An authenticated attacker with low privileges can craft a malicious HTTP request to the /goform/DhcpListClient endpoint with a manipulated page argument. The attack requires no user interaction and can be executed against any reachable Tenda 4G06 device running the vulnerable firmware version.

The vulnerability affects the confidentiality, integrity, and availability of the target system, as successful exploitation could allow an attacker to:

• Execute arbitrary code with router privileges
• Modify router configuration and redirect traffic
• Cause denial of service by crashing the device
• Establish persistent backdoor access to the network

The vulnerability is triggered through the router's HTTP endpoint. When a crafted request with an oversized page parameter is sent to /goform/DhcpListClient, the fromDhcpListClient function fails to properly validate the input length before copying it to a stack buffer. This overflow condition corrupts stack memory and can be leveraged to gain control of program execution. For detailed technical analysis, refer to the GitHub CVE Issue and VulDB entry #353962.

Detection Methods for CVE-2026-5036

Indicators of Compromise

• Unusual HTTP requests to /goform/DhcpListClient with abnormally large page parameter values
• Router crashes or unexpected reboots without apparent cause
• Unauthorized configuration changes to the Tenda 4G06 device
• Suspicious outbound network connections originating from the router

Detection Strategies

• Monitor HTTP traffic to the router management interface for requests containing oversized parameters to /goform/DhcpListClient
• Deploy network intrusion detection rules to identify buffer overflow exploitation attempts against Tenda devices
• Implement logging on network segments where Tenda 4G06 routers are deployed to capture abnormal traffic patterns
• Use SentinelOne Singularity to detect and block exploitation attempts targeting network infrastructure devices

Monitoring Recommendations

• Enable logging on firewall rules protecting router management interfaces
• Configure alerts for repeated failed authentication attempts followed by successful access to the vulnerable endpoint
• Monitor router uptime and investigate any unexpected service interruptions
• Review router access logs for requests with unusual parameter lengths or encoding

How to Mitigate CVE-2026-5036

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only
• Disable remote management if not strictly required for operations
• Place the Tenda 4G06 router behind a firewall that filters malicious requests
• Monitor for firmware updates from Tenda and apply patches as soon as available

Patch Information

At the time of this publication, no official patch has been released by Tenda for this vulnerability. Organizations should monitor the Tenda Security Homepage for firmware updates addressing CVE-2026-5036. In the absence of an official fix, implementing the workarounds and access restrictions described below is critical for reducing exposure.

Workarounds

• Implement network segmentation to isolate the Tenda 4G06 router from sensitive network resources
• Configure firewall rules to block external access to the /goform/DhcpListClient endpoint
• Use a VPN for remote management instead of exposing the web interface directly
• Consider replacing the affected device with an alternative router if a patch is not released in a timely manner

# Example iptables rule to restrict access to router management interface
# Replace 192.168.1.1 with your router's IP and 192.168.1.100 with trusted admin IP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -s 192.168.1.100 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT