CVE-2025-63457: Tenda AX1803 Firmware DoS Vulnerability

CVE-2025-63457 Overview

A stack overflow vulnerability has been discovered in Tenda AX-1803 wireless router firmware version 1.0.0.1. The vulnerability exists within the sub_4F55C function, which improperly handles the wanMTU parameter. Attackers can exploit this flaw to cause a Denial of Service (DoS) condition by sending specially crafted requests to the affected device.

Critical Impact

This vulnerability allows remote unauthenticated attackers to crash affected Tenda AX-1803 routers, disrupting network connectivity for all connected devices.

Affected Products

• Tenda AX-1803 firmware version 1.0.0.1
• Tenda AX-1803 hardware devices running vulnerable firmware

Discovery Timeline

• 2025-11-10 - CVE-2025-63457 published to NVD
• 2025-11-18 - Last updated in NVD database

Technical Details for CVE-2025-63457

Vulnerability Analysis

This vulnerability is classified as a stack overflow (CWE-787: Out-of-bounds Write, CWE-121: Stack-based Buffer Overflow). The flaw resides in the sub_4F55C function within the Tenda AX-1803 firmware, which processes the wanMTU parameter without proper bounds checking.

When a malicious request containing an oversized or specially crafted wanMTU value is submitted to the router's web interface, the function fails to validate the input length before copying it to a stack buffer. This results in data being written beyond the allocated buffer boundaries, corrupting adjacent stack memory and causing the device to crash.

The vulnerability is particularly concerning because it can be exploited remotely over the network without requiring authentication, making any exposed Tenda AX-1803 router a potential target.

Root Cause

The root cause of this vulnerability is improper input validation in the sub_4F55C function. The function accepts the wanMTU parameter from user-controlled input without verifying that the data length does not exceed the size of the destination stack buffer. This is a classic stack-based buffer overflow scenario where user input directly influences memory operations without adequate sanitization.

Attack Vector

The attack vector is network-based, allowing remote exploitation. An attacker can craft a malicious HTTP request targeting the router's web management interface with an oversized or malformed wanMTU parameter value. Upon processing this request, the vulnerable sub_4F55C function overflows its stack buffer, leading to a denial of service condition.

The attack does not require authentication, making it accessible to any attacker who can reach the router's management interface. If the management interface is exposed to the internet (a common misconfiguration), the router becomes vulnerable to attacks from anywhere on the internet.

For technical details on the vulnerability, see the GitHub Vulnerability Report published by the security researcher.

Detection Methods for CVE-2025-63457

Indicators of Compromise

• Unexpected router reboots or crashes without apparent cause
• Network connectivity disruptions affecting all connected devices
• Unusual HTTP requests to the router's web interface containing abnormally large wanMTU parameter values
• Repeated access attempts to router configuration endpoints from external IP addresses

Detection Strategies

• Monitor network traffic for HTTP requests with unusually large parameter values targeting router management interfaces
• Implement intrusion detection rules to flag requests containing the wanMTU parameter with suspicious payload sizes
• Deploy network-based anomaly detection to identify patterns consistent with DoS exploitation attempts
• Review router logs for evidence of unexpected restarts or service interruptions

Monitoring Recommendations

• Enable logging on network perimeter devices to capture traffic destined for router management ports
• Implement alerting for repeated failed requests or connection attempts to router administration interfaces
• Monitor router availability and uptime metrics to detect service disruptions indicative of exploitation
• Consider using SentinelOne Singularity for network visibility and threat detection capabilities

How to Mitigate CVE-2025-63457

Immediate Actions Required

• Disable remote management access to the Tenda AX-1803 router immediately if not required
• Restrict access to the router's web management interface to trusted internal IP addresses only
• Implement firewall rules to block external access to the router's administrative ports
• Monitor for firmware updates from Tenda and apply patches as soon as they become available

Patch Information

At the time of this publication, no official patch has been released by Tenda for this vulnerability. Users should monitor Tenda's official support channels for security updates addressing CVE-2025-63457. Until a patch is available, implementing the workarounds below is strongly recommended.

Workarounds

• Disable the WAN-side management interface to prevent remote exploitation from the internet
• Configure access control lists (ACLs) to restrict management interface access to specific trusted IP addresses
• Place the router behind an additional firewall that filters incoming traffic to management ports
• Consider replacing vulnerable devices with alternative hardware if critical network availability is required

# Example: Restrict management interface access via iptables on upstream firewall
# Block external access to common router management ports
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 443 -j DROP
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 8080 -j DROP

# Allow management access only from trusted admin network
iptables -I FORWARD -s <TRUSTED_ADMIN_SUBNET> -d <ROUTER_IP> -p tcp --dport 80 -j ACCEPT