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

bash

# 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