CVE-2025-4368: Tenda AC8 Buffer Overflow Vulnerability

CVE-2025-4368 Overview

A critical buffer overflow vulnerability has been discovered in Tenda AC8 router firmware version 16.03.34.06. The vulnerability exists in the formGetRouterStatus function within the /goform/MtuSetMacWan file, where improper handling of the shareSpeed argument allows attackers to trigger a buffer overflow condition. This network-accessible vulnerability can be exploited remotely by authenticated attackers to compromise the affected device.

Critical Impact

Remote attackers with low-level privileges can exploit this buffer overflow to potentially achieve code execution on vulnerable Tenda AC8 routers, leading to complete device compromise including confidentiality, integrity, and availability impacts.

Affected Products

• Tenda AC8 Firmware version 16.03.34.06
• Tenda AC8 Hardware Device

Discovery Timeline

• 2025-05-06 - CVE-2025-4368 published to NVD
• 2025-05-13 - Last updated in NVD database

Technical Details for CVE-2025-4368

Vulnerability Analysis

This vulnerability is categorized under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) and CWE-120 (Buffer Copy without Checking Size of Input). The flaw exists in the formGetRouterStatus function, which processes user-controlled input through the shareSpeed argument without proper bounds checking.

When a malicious request is sent to the /goform/MtuSetMacWan endpoint with a specially crafted shareSpeed parameter value, the function fails to validate the input length before copying it into a fixed-size buffer. This classic buffer overflow condition allows an attacker to overwrite adjacent memory locations, potentially corrupting program execution flow.

The vulnerability is accessible over the network, meaning any attacker who can reach the router's web management interface can attempt exploitation. The publicly disclosed exploit information increases the risk of active exploitation attempts against unpatched devices.

Root Cause

The root cause of this vulnerability is insufficient input validation in the formGetRouterStatus function. The code fails to verify that the length of the shareSpeed argument does not exceed the allocated buffer size before performing memory copy operations. This absence of boundary checking is a fundamental coding error that leads to the classic stack-based or heap-based buffer overflow condition.

Attack Vector

The attack can be launched remotely over the network by sending a malicious HTTP request to the vulnerable endpoint /goform/MtuSetMacWan. The attacker must have low-level authentication (likely access to the router's web interface) but requires no user interaction to exploit the vulnerability.

An attacker would craft a request containing an excessively long shareSpeed parameter value. When the formGetRouterStatus function processes this input, the oversized data overflows the destination buffer, potentially allowing the attacker to control program execution, inject shellcode, or cause a denial of service condition.

For technical details regarding the exploitation mechanism, refer to the GitHub PoC Repository and VulDB CVE Analysis.

Detection Methods for CVE-2025-4368

Indicators of Compromise

• Unexpected reboots or instability of the Tenda AC8 router
• Unusual network traffic patterns originating from or destined to the router's management interface
• HTTP requests to /goform/MtuSetMacWan with abnormally large shareSpeed parameter values
• Evidence of unauthorized configuration changes on the router

Detection Strategies

• Monitor HTTP traffic to the router's web management interface for requests targeting /goform/MtuSetMacWan
• Implement intrusion detection rules to alert on oversized parameter values in form submissions to Tenda router endpoints
• Review router access logs for repeated or unusual access patterns to the vulnerable endpoint
• Deploy network-based anomaly detection to identify exploitation attempts

Monitoring Recommendations

• Restrict access to the router's web management interface to trusted networks only
• Enable logging on the router if available and forward logs to a centralized SIEM for analysis
• Monitor for unusual outbound connections from the router that may indicate post-exploitation activity
• Regularly audit router configurations for unauthorized changes

How to Mitigate CVE-2025-4368

Immediate Actions Required

• Check if your Tenda AC8 router is running firmware version 16.03.34.06 and prioritize for remediation
• Restrict network access to the router's web management interface using firewall rules
• Disable remote management features if not required
• Monitor for any vendor-released patches on the Tenda Official Website

Patch Information

As of the last update on 2025-05-13, no official patch has been confirmed by the vendor. Organizations should monitor Tenda's official website for firmware updates addressing this vulnerability. Consider replacing vulnerable devices with alternative products if patches are not made available in a timely manner.

Workarounds

• Limit access to the router's management interface to trusted internal networks only using network segmentation
• Place the router behind a firewall that can filter malicious requests to the vulnerable endpoint
• Disable WAN-side access to the management interface if enabled
• Consider deploying a network intrusion prevention system (IPS) to block exploitation attempts

# Example iptables rules to restrict access to router management interface
# Replace 192.168.1.1 with your router's IP and 192.168.1.0/24 with trusted network

# Allow management access only from trusted network
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP

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