CVE-2025-63456: Tenda AX1803 Firmware DoS Vulnerability

CVE-2025-63456 Overview

A stack overflow vulnerability has been identified in the Tenda AX-1803 wireless router firmware version 1.0.0.1. The vulnerability exists in the SetSysTimeCfg function, where the time parameter is improperly handled, allowing attackers to trigger a stack-based buffer overflow. This flaw enables remote attackers to cause a Denial of Service (DoS) condition on affected devices through specially crafted HTTP requests, potentially disrupting network connectivity for all connected users.

Critical Impact

Remote attackers can crash vulnerable Tenda AX-1803 routers without authentication, causing complete loss of network services for connected devices.

Affected Products

• Tenda AX1803 Firmware version 1.0.0.1
• Tenda AX1803 Hardware

Discovery Timeline

• 2025-11-10 - CVE-2025-63456 published to NVD
• 2025-11-18 - Last updated in NVD database

Technical Details for CVE-2025-63456

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-bounds Write) and CWE-121 (Stack-based Buffer Overflow). The flaw resides in the SetSysTimeCfg function within the Tenda AX-1803 router's web management interface. When processing the time parameter, the function fails to adequately validate the length of user-supplied input before copying it to a fixed-size stack buffer.

The attack can be executed remotely over the network without requiring authentication or user interaction. While this vulnerability does not allow direct compromise of confidentiality or integrity, it enables complete disruption of the router's availability. An attacker can repeatedly exploit this vulnerability to maintain a persistent denial of service condition against the target device.

Root Cause

The root cause of CVE-2025-63456 is improper bounds checking in the SetSysTimeCfg function. The time parameter is copied to a stack-allocated buffer without verifying that the input length does not exceed the buffer's capacity. This allows an attacker to overwrite adjacent stack memory, corrupting the stack frame and causing the router to crash.

This is a common vulnerability pattern in embedded device firmware where memory-safe programming practices are not followed, and user input from HTTP request parameters is processed without adequate validation.

Attack Vector

The attack is executed remotely via the network through the router's HTTP-based web management interface. An attacker sends a crafted HTTP request to the SetSysTimeCfg endpoint containing an oversized time parameter value. When the vulnerable function processes this request, the oversized input overflows the stack buffer, corrupting the return address and other critical stack data, ultimately causing the device to crash and restart.

The attack requires no authentication and no user interaction, making it particularly dangerous for devices exposed to untrusted networks. Technical details regarding the specific exploitation technique are documented in the GitHub vulnerability documentation.

Detection Methods for CVE-2025-63456

Indicators of Compromise

• Unexpected router reboots or repeated device crashes
• Network service interruptions coinciding with suspicious HTTP traffic to router management interface
• HTTP requests to the SetSysTimeCfg endpoint with abnormally large time parameter values
• Elevated volume of requests targeting the router's web management interface from external sources

Detection Strategies

• Monitor network traffic for HTTP requests to the router's management interface containing unusually large parameter values
• Implement IDS/IPS rules to detect oversized payloads in HTTP requests targeting known vulnerable endpoints
• Configure alerting for unexpected router reboots or service interruptions that may indicate exploitation attempts
• Use network segmentation to isolate router management interfaces from untrusted networks

Monitoring Recommendations

• Enable logging on the router's management interface if available to capture suspicious request patterns
• Deploy network monitoring solutions capable of inspecting HTTP traffic to embedded device management interfaces
• Establish baseline behavior for router operations to detect anomalous activity indicative of DoS attacks
• Monitor for multiple consecutive connection attempts to the router management interface from single sources

How to Mitigate CVE-2025-63456

Immediate Actions Required

• Restrict access to the Tenda AX-1803 web management interface to trusted networks only
• Disable remote management features if not required for operations
• Implement firewall rules to block external access to the router's HTTP management port (typically port 80)
• Consider replacing vulnerable devices with alternative hardware if no patch is available

Patch Information

At the time of this publication, no official security patch from Tenda has been identified for CVE-2025-63456. Organizations should monitor Tenda's official support channels and firmware download pages for security updates addressing this vulnerability. The GitHub vulnerability documentation provides additional technical details about the vulnerability.

Workarounds

• Restrict management interface access to specific trusted IP addresses using ACLs or firewall rules
• Disable the web-based management interface entirely if CLI or other management methods are available
• Place the router behind an additional firewall that can filter and block malicious HTTP requests
• Implement network segmentation to prevent untrusted devices from accessing the router management interface

# Example: Block external access to router management interface using iptables on upstream firewall
iptables -A FORWARD -p tcp --dport 80 -d <router_ip> -j DROP
iptables -A FORWARD -p tcp --dport 443 -d <router_ip> -j DROP

# Allow management access only from trusted admin workstation
iptables -I FORWARD -p tcp --dport 80 -s <admin_ip> -d <router_ip> -j ACCEPT