CVE-2024-2806: Tenda AC15 Buffer Overflow Vulnerability

CVE-2024-2806 Overview

A critical stack-based buffer overflow vulnerability has been discovered in Tenda AC15 routers running firmware versions 15.03.05.18 and 15.03.20_multi. This vulnerability exists in the addWifiMacFilter function located in the /goform/addWifiMacFilter endpoint. Remote attackers can exploit this flaw by manipulating the deviceId or deviceMac arguments, potentially leading to remote code execution or complete device compromise.

Critical Impact

This vulnerability allows unauthenticated remote attackers to execute arbitrary code on affected Tenda AC15 routers, potentially gaining complete control over the network device and enabling further attacks on connected systems.

Affected Products

• Tenda AC15 Firmware version 15.03.05.18
• Tenda AC15 Firmware version 15.03.05.20_multi
• Tenda AC15 Hardware version 1.0

Discovery Timeline

• 2024-03-22 - CVE-2024-2806 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-2806

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow), a memory corruption issue that occurs when the addWifiMacFilter function fails to properly validate the length of user-supplied input in the deviceId and deviceMac parameters. When an attacker sends an oversized payload through the web management interface at /goform/addWifiMacFilter, the function copies this data onto the stack without adequate bounds checking, causing the buffer to overflow.

The exploitation can be performed remotely over the network without requiring any authentication or user interaction. An attacker who successfully exploits this vulnerability could overwrite critical stack data including return addresses, potentially redirecting execution flow to attacker-controlled code.

Root Cause

The root cause of this vulnerability lies in unsafe memory handling within the addWifiMacFilter function. The firmware uses insecure string copy operations that do not properly validate or limit the length of the deviceId and deviceMac input parameters before copying them to fixed-size stack buffers. This lack of input validation is a common weakness in embedded IoT device firmware where security best practices are often overlooked during development.

Attack Vector

The attack can be initiated remotely over the network by sending a specially crafted HTTP request to the vulnerable /goform/addWifiMacFilter endpoint on the router's web management interface. The attacker would craft a malicious request containing an oversized deviceId or deviceMac parameter designed to overflow the stack buffer and overwrite the return address. Since no authentication is required to access this endpoint, any attacker with network access to the router's management interface can attempt exploitation.

The vulnerability mechanism involves sending malformed input to the MAC filter functionality of the router's web interface. When the addWifiMacFilter function processes the oversized deviceId or deviceMac parameters, the stack buffer is overwritten beyond its intended boundaries. Technical details of the vulnerable code path are documented in the GitHub Vulnerability Documentation.

Detection Methods for CVE-2024-2806

Indicators of Compromise

• Unexpected HTTP POST requests to /goform/addWifiMacFilter with unusually large deviceId or deviceMac parameter values
• Router crashes, unexpected reboots, or instability following network requests to the management interface
• Anomalous outbound connections from the router to unknown external IP addresses
• Unusual changes to router configuration or firmware settings

Detection Strategies

• Monitor HTTP traffic to the router's web management interface for requests containing abnormally long parameter values in the deviceId or deviceMac fields
• Implement network intrusion detection rules to alert on POST requests to /goform/addWifiMacFilter with payload sizes exceeding normal operational parameters
• Deploy network segmentation to isolate router management interfaces from untrusted network segments
• Enable logging on the router if available and monitor for signs of exploitation attempts or crashes

Monitoring Recommendations

• Restrict access to the router's web management interface to trusted IP addresses only
• Regularly review network logs for suspicious activity targeting router endpoints
• Implement automated alerts for router crashes or unexpected configuration changes
• Consider deploying a network-based anomaly detection system to identify unusual traffic patterns targeting IoT devices

How to Mitigate CVE-2024-2806

Immediate Actions Required

• Disable remote management access to the Tenda AC15 router's web interface immediately
• Restrict access to the router's management interface to only trusted internal networks using firewall rules
• Monitor network traffic for any suspicious activity targeting the /goform/addWifiMacFilter endpoint
• Consider replacing the affected device with a router from a vendor with better security support practices

Patch Information

At the time of disclosure, no official patch has been released by Tenda. The vendor was contacted early about this vulnerability but did not respond. Users should monitor Tenda's official website for any security updates. Given the vendor's lack of response, organizations using affected Tenda AC15 routers should strongly consider migrating to alternative hardware with active security support.

For additional technical details, refer to the VulDB advisory and the vulnerability documentation on GitHub.

Workarounds

• Disable the web management interface entirely if not required for operations
• Place the router behind a firewall that blocks external access to management ports
• Use network access control lists (ACLs) to restrict which devices can communicate with the router's management interface
• Implement network segmentation to isolate the vulnerable router from critical systems

# Example firewall rule to block external access to router management interface
# Adjust IP addresses and interface names for your environment
iptables -A INPUT -i eth0 -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -i eth0 -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP