CVE-2025-69763: Tenda AX3 Firmware RCE Vulnerability

CVE-2025-69763 Overview

CVE-2025-69763 is a stack overflow vulnerability affecting Tenda AX3 firmware version 16.03.12.11. The vulnerability exists in the formSetIptv function and can be triggered through the vlanId parameter. Successful exploitation leads to memory corruption and enables remote code execution, allowing attackers to gain complete control over the affected device without authentication.

Critical Impact

This firmware vulnerability allows unauthenticated remote attackers to execute arbitrary code on Tenda AX3 routers, potentially compromising the entire network infrastructure connected to the device.

Affected Products

• Tenda AX3 Router
• Firmware version 16.03.12.11

Discovery Timeline

• 2026-01-21 - CVE-2025-69763 published to NVD
• 2026-01-22 - Last updated in NVD database

Technical Details for CVE-2025-69763

Vulnerability Analysis

This vulnerability is classified under CWE-121 (Stack-based Buffer Overflow). The formSetIptv function in the Tenda AX3 firmware fails to properly validate the length of user-supplied input passed through the vlanId parameter. When an attacker supplies an oversized value, the function writes beyond the allocated stack buffer boundaries, corrupting adjacent memory regions including the return address and saved registers.

The network-accessible nature of this vulnerability means attackers can exploit it remotely without requiring any authentication or user interaction. The attack complexity is low, making this an attractive target for threat actors seeking to compromise home and small business network infrastructure.

Root Cause

The root cause is improper bounds checking in the formSetIptv function when processing the vlanId parameter. The firmware uses unsafe string handling functions that copy user input directly to a fixed-size stack buffer without validating input length against buffer capacity. This allows attackers to overflow the stack buffer and overwrite critical control flow data.

Attack Vector

The attack vector is network-based, targeting the router's web management interface. An attacker can craft a malicious HTTP request containing an oversized vlanId parameter value. When the formSetIptv function processes this request, the overflow occurs, enabling the attacker to:

1. Corrupt the stack frame including the saved return address
2. Redirect execution to attacker-controlled shellcode
3. Achieve remote code execution with the privileges of the web server process (typically root on embedded devices)

The vulnerability does not require authentication, meaning any attacker with network access to the device's management interface can attempt exploitation.

For detailed technical analysis of this vulnerability, refer to the Notion Analysis of Tenda AX3 Vulnerability.

Detection Methods for CVE-2025-69763

Indicators of Compromise

• Unusual outbound network connections from the router to unknown IP addresses
• Unexpected reboots or instability of Tenda AX3 devices
• Modified firmware or configuration files on the device
• HTTP access logs showing abnormally long vlanId parameter values in requests to formSetIptv

Detection Strategies

• Monitor network traffic for HTTP requests to Tenda AX3 management interfaces containing oversized parameter values
• Implement network segmentation to isolate IoT and router management interfaces from untrusted networks
• Deploy IDS/IPS rules to detect stack overflow exploitation patterns targeting embedded devices
• Analyze router logs for unusual administrative access attempts

Monitoring Recommendations

• Enable logging on the router management interface and forward logs to a centralized SIEM
• Monitor for firmware integrity changes using cryptographic hash verification
• Set up alerts for access attempts to the router management interface from external networks
• Conduct periodic vulnerability assessments of network edge devices

How to Mitigate CVE-2025-69763

Immediate Actions Required

• Disable remote management access to the Tenda AX3 router from the WAN interface
• Restrict access to the router's web management interface to trusted internal networks only
• Implement firewall rules to block external access to the device's management ports
• Check Tenda's official website for firmware updates that address this vulnerability

Patch Information

At the time of publication, no official patch has been confirmed for this vulnerability. Organizations should monitor Tenda's security advisories for firmware updates addressing CVE-2025-69763. Until a patch is available, implement the recommended workarounds to reduce exposure.

Workarounds

• Disable the IPTV configuration feature if not in use
• Place the router management interface behind a VPN for remote administration needs
• Implement network access controls to limit which hosts can reach the management interface
• Consider replacing vulnerable devices with alternative hardware if no patch becomes available

# Firewall rule example to restrict management access (if router supports custom rules)
# Block external access to management interface
iptables -A INPUT -i wan0 -p tcp --dport 80 -j DROP
iptables -A INPUT -i wan0 -p tcp --dport 443 -j DROP