CVE-2025-71025: Tenda AX-3 Stack Overflow DoS Vulnerability

CVE-2025-71025 Overview

A stack overflow vulnerability has been discovered in the Tenda AX-3 router firmware version 16.03.12.10_CN. The vulnerability exists within the fromAdvSetMacMtuWan function, specifically in the handling of the cloneType2 parameter. When processing a specially crafted request, the function fails to properly validate input boundaries, leading to a stack-based buffer overflow condition. This vulnerability allows remote attackers to cause a Denial of Service (DoS) by sending malicious requests to the affected device.

Critical Impact

Remote attackers can crash the Tenda AX-3 router by exploiting the stack overflow in the cloneType2 parameter, causing network disruption for all connected devices.

Affected Products

• Tenda AX-3 Router
• Firmware version 16.03.12.10_CN

Discovery Timeline

• 2026-01-13 - CVE-2025-71025 published to NVD
• 2026-01-13 - Last updated in NVD database

Technical Details for CVE-2025-71025

Vulnerability Analysis

The vulnerability is a classic stack overflow condition that occurs in the fromAdvSetMacMtuWan function of the Tenda AX-3 router firmware. This function is responsible for handling WAN configuration settings related to MAC address cloning and MTU settings. The cloneType2 parameter is passed to this function without adequate bounds checking, allowing an attacker to overflow the stack buffer allocated for processing this input.

Stack overflow vulnerabilities in embedded devices like routers are particularly concerning because these devices often lack modern exploit mitigations such as stack canaries, ASLR, or NX bit protections. The firmware running on the Tenda AX-3 processes HTTP requests through its web management interface, making this vulnerability remotely exploitable by any attacker who can reach the router's administration interface.

Root Cause

The root cause of this vulnerability is improper input validation in the fromAdvSetMacMtuWan function. The function allocates a fixed-size buffer on the stack for the cloneType2 parameter but does not verify that the incoming data fits within the allocated space. When an attacker supplies an oversized value for this parameter, the data overwrites adjacent stack memory, corrupting the function's stack frame and causing the device to crash.

Attack Vector

The attack can be executed remotely by sending a crafted HTTP request to the router's web management interface. The attacker constructs a request that includes an excessively long cloneType2 parameter value, which triggers the stack overflow when processed by the fromAdvSetMacMtuWan function. No authentication may be required depending on the router's configuration, as some Tenda devices expose certain functions without proper access controls.

The attack results in a Denial of Service condition where the router becomes unresponsive, requiring a manual power cycle to restore functionality. While the current analysis confirms DoS capability, stack overflow vulnerabilities may potentially be leveraged for code execution if further exploit development is pursued.

For detailed technical analysis, refer to the GitHub Vulnerability Report.

Detection Methods for CVE-2025-71025

Indicators of Compromise

• Unexpected router reboots or unresponsive states without apparent cause
• Unusual HTTP POST requests to WAN configuration endpoints containing abnormally large parameter values
• Repeated connection attempts to the router's management interface from external IP addresses
• Network connectivity loss followed by router crashes

Detection Strategies

• Monitor HTTP traffic to the router's management interface for requests with unusually large cloneType2 parameter values
• Implement intrusion detection rules to flag POST requests to /goform/ endpoints with payload sizes exceeding normal thresholds
• Configure network monitoring to alert on router availability issues or unexpected device restarts
• Review router access logs for patterns indicating exploitation attempts

Monitoring Recommendations

• Enable logging on the Tenda AX-3 if supported and forward logs to a central SIEM for analysis
• Implement network segmentation to isolate router management interfaces from untrusted networks
• Deploy network-based intrusion detection systems to monitor traffic patterns to IoT and network devices
• Regularly check router uptime and stability metrics to detect potential DoS attack indicators

How to Mitigate CVE-2025-71025

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only
• Disable remote management access if not required for operations
• Place the router's management interface on a separate VLAN inaccessible from the general network
• Monitor for firmware updates from Tenda that address this vulnerability
• Consider replacing the affected device with a router from a vendor with better security update practices

Patch Information

No official patch is currently available from Tenda for this vulnerability. Users should monitor the vendor's official website and support channels for firmware updates. Given the nature of IoT device support cycles, affected users should consider implementing network-level mitigations while awaiting an official fix.

The vulnerability was documented in a GitHub Vulnerability Report which provides additional technical details.

Workarounds

• Disable the WAN configuration interface entirely if the router's WAN settings do not require modification
• Implement firewall rules on upstream devices to block access to the router's management ports (typically 80/443)
• Use access control lists (ACLs) to limit management interface access to specific administrator workstations
• Deploy a separate firewall or security appliance in front of the affected router to filter malicious requests
• Consider network segmentation to minimize the impact of a successful DoS attack on the router

# Example iptables rules to restrict management access (apply on upstream firewall)
# Block external access to router management interface
iptables -A FORWARD -d ROUTER_IP -p tcp --dport 80 -j DROP
iptables -A FORWARD -d ROUTER_IP -p tcp --dport 443 -j DROP

# Allow management access only from trusted admin subnet
iptables -I FORWARD -s ADMIN_SUBNET -d ROUTER_IP -p tcp --dport 80 -j ACCEPT
iptables -I FORWARD -s ADMIN_SUBNET -d ROUTER_IP -p tcp --dport 443 -j ACCEPT