CVE-2025-12618: Tenda AC8 Buffer Overflow Vulnerability

CVE-2025-12618 Overview

A buffer overflow vulnerability has been identified in Tenda AC8 router firmware version 16.03.34.06. This vulnerability affects the /goform/DatabaseIniSet endpoint, where improper handling of the Time argument leads to a classic buffer overflow condition. The flaw can be exploited remotely by authenticated attackers, potentially allowing complete compromise of the affected device.

Critical Impact

Remote attackers with low privileges can exploit this buffer overflow to achieve high-impact compromise of confidentiality, integrity, and availability on affected Tenda AC8 routers.

Affected Products

• Tenda AC8 Firmware version 16.03.34.06
• Tenda AC8 Hardware version 4.0
• Tenda AC8 routers running vulnerable firmware

Discovery Timeline

• 2025-11-03 - CVE-2025-12618 published to NVD
• 2025-11-05 - Last updated in NVD database

Technical Details for CVE-2025-12618

Vulnerability Analysis

This vulnerability is a buffer overflow (CWE-120) stemming from improper restriction of operations within memory buffer bounds (CWE-119). The vulnerable endpoint /goform/DatabaseIniSet accepts user-controlled input via the Time parameter without adequate bounds checking.

When an attacker submits a specially crafted request with an oversized Time argument, the application writes data beyond the allocated buffer boundaries. This memory corruption can overwrite adjacent memory regions, including stack return addresses or function pointers, potentially leading to arbitrary code execution with the privileges of the web server process.

The network-accessible nature of this vulnerability, combined with the low complexity required for exploitation, makes it particularly dangerous for exposed devices. The exploit has been publicly disclosed, increasing the risk of active exploitation in the wild.

Root Cause

The root cause of CVE-2025-12618 is insufficient input validation in the DatabaseIniSet function handler. The firmware fails to properly validate the length of the Time parameter before copying it into a fixed-size buffer. This classic buffer overflow pattern occurs when:

1. A fixed-size stack or heap buffer is allocated for the Time parameter
2. User input is copied into this buffer without length verification
3. Input exceeding the buffer size overwrites adjacent memory

This represents a fundamental secure coding failure where untrusted input is processed without proper bounds checking.

Attack Vector

The attack vector is network-based, requiring the attacker to send malicious HTTP requests to the router's web management interface. The exploitation process involves:

1. Gaining low-privilege access to the router's web interface (authentication required)
2. Crafting a POST request to /goform/DatabaseIniSet with an oversized Time parameter
3. The oversized input triggers the buffer overflow, corrupting adjacent memory
4. Successful exploitation can lead to denial of service or potentially arbitrary code execution

The vulnerability can be triggered remotely by any authenticated user, making it exploitable across the network without physical access to the device. Additional technical details are available in the VulDB entry and the Yuque technical writeup.

Detection Methods for CVE-2025-12618

Indicators of Compromise

• Unusual HTTP POST requests to /goform/DatabaseIniSet with abnormally large Time parameter values
• Router crashes or unexpected reboots following web interface access
• Anomalous network traffic patterns originating from the router
• Unexpected modifications to router configuration or firmware

Detection Strategies

• Monitor web server logs for requests to /goform/DatabaseIniSet with suspicious payload sizes
• Implement network intrusion detection rules to flag oversized HTTP parameters targeting Tenda management endpoints
• Deploy firmware integrity monitoring to detect unauthorized modifications
• Configure alerting for repeated authentication failures followed by management interface access

Monitoring Recommendations

• Enable logging on all Tenda AC8 router management interfaces
• Implement network segmentation to isolate router management traffic
• Deploy network monitoring solutions to detect anomalous traffic patterns to/from router devices
• Regularly audit authentication logs for unauthorized access attempts

How to Mitigate CVE-2025-12618

Immediate Actions Required

• Restrict access to the router web management interface to trusted networks only
• Disable remote management if not required for operations
• Implement network segmentation to isolate affected devices
• Monitor for exploitation attempts targeting the vulnerable endpoint
• Review and update router administrative credentials

Patch Information

At the time of publication, no official patch has been released by Tenda. Users should monitor the Tenda official website for firmware updates addressing this vulnerability. Check for firmware versions newer than 16.03.34.06 that specifically mention security fixes for buffer overflow vulnerabilities.

Workarounds

• Disable the web management interface or restrict it to local LAN access only
• Place affected routers behind a firewall that blocks external access to management ports
• Implement access control lists (ACLs) to limit which IP addresses can reach the management interface
• Consider replacing vulnerable devices with supported alternatives if no patch becomes available

# Example: Restrict management interface access via firewall rules
# Block external access to router management port (typically 80/443)
iptables -A INPUT -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP