CVE-2025-70651: Tenda AX-1803 Stack Overflow DoS Vulnerability

CVE-2025-70651 Overview

A stack overflow vulnerability has been discovered in the Tenda AX-1803 wireless router firmware version 1.0.0.1. The vulnerability exists in the ssid parameter of the form_fast_setting_wifi_set function, which fails to properly validate input length before copying data to a fixed-size stack buffer. This memory corruption flaw allows remote attackers to cause a Denial of Service (DoS) condition by sending specially crafted requests to the affected device.

Critical Impact

Remote attackers can crash the Tenda AX-1803 router without authentication, causing network disruption for all connected devices.

Affected Products

• Tenda AX-1803 v1.0.0.1
• Tenda AX-1803 firmware versions prior to security patch

Discovery Timeline

• 2026-01-21 - CVE-2025-70651 published to NVD
• 2026-01-21 - Last updated in NVD database

Technical Details for CVE-2025-70651

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow), a memory corruption issue that occurs when data is written beyond the boundaries of a fixed-size stack buffer. The vulnerable function form_fast_setting_wifi_set handles WiFi configuration requests and processes the ssid parameter without adequate bounds checking. When an attacker submits a request containing an oversized ssid value, the data overflows the allocated buffer on the stack, corrupting adjacent memory regions.

The attack can be executed remotely over the network without requiring any authentication or user interaction. While this particular vulnerability results in denial of service through device crash, stack overflow vulnerabilities of this nature can potentially be leveraged for more severe attacks depending on the memory layout and security mitigations present in the firmware.

Root Cause

The root cause of this vulnerability lies in the improper handling of user-supplied input in the form_fast_setting_wifi_set function. The function allocates a fixed-size buffer on the stack for the ssid parameter but does not validate the length of incoming data before copying it into this buffer. This is a common programming error in embedded device firmware where memory-safe functions are not consistently used for string operations.

Attack Vector

The vulnerability is exploited via network-based requests to the router's web management interface. An attacker sends a crafted HTTP request containing an excessively long ssid parameter to the form_fast_setting_wifi_set endpoint. The malicious payload overflows the stack buffer, corrupting the return address or other critical stack data, which leads to a crash when the function attempts to return. No authentication is required to trigger this condition, making it accessible to any attacker who can reach the device's management interface.

The attack mechanism involves:

1. Identifying a Tenda AX-1803 router accessible on the network
2. Crafting a request with an oversized ssid parameter value
3. Sending the request to the WiFi configuration endpoint
4. The stack overflow causes the device to crash and reboot

Technical details and proof-of-concept information are available in the GitHub Vulnerability Report.

Detection Methods for CVE-2025-70651

Indicators of Compromise

• Unexpected router reboots or service interruptions
• HTTP requests to WiFi configuration endpoints with abnormally large ssid parameter values
• Network traffic patterns showing repeated requests to form_fast_setting_wifi_set endpoints
• System logs indicating memory corruption or segmentation faults on the affected device

Detection Strategies

• Monitor network traffic for HTTP requests containing unusually large ssid parameters (e.g., exceeding 32 characters)
• Implement intrusion detection rules to flag requests to WiFi configuration endpoints with oversized input values
• Deploy network monitoring to detect repeated connection attempts to router management interfaces from unusual sources
• Configure alerting for unexpected device reboots or availability issues

Monitoring Recommendations

• Enable logging on network firewalls and IDS/IPS systems for traffic to router management ports
• Monitor router uptime and availability metrics to detect crash-and-reboot patterns
• Review access logs for the router's web management interface regularly
• Segment management interfaces to separate VLANs and monitor cross-VLAN traffic anomalies

How to Mitigate CVE-2025-70651

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only
• Disable remote management functionality if not required
• Place the router behind a firewall that blocks external access to management ports
• Monitor the vendor's website for firmware updates addressing this vulnerability
• Consider temporarily replacing affected devices in high-security environments until a patch is available

Patch Information

At the time of publication, no official patch has been released by Tenda for this vulnerability. Organizations should monitor Tenda's support channels and the GitHub Vulnerability Report for updates on remediation status. Until a patch is available, implementing the workarounds below is strongly recommended.

Workarounds

• Configure firewall rules to restrict management interface access to specific trusted IP addresses
• Disable the web-based management interface and use alternative configuration methods if available
• Implement network segmentation to isolate affected devices from untrusted networks
• Deploy a web application firewall (WAF) in front of the management interface to filter malicious requests

# Example firewall rule to restrict management access (iptables)
# Allow management access only from trusted admin workstation
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.100 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP

# Block external access to management interface on WAN
iptables -A INPUT -i eth0 -p tcp --dport 80 -j DROP