CVE-2024-32318: Tenda AC500 Buffer Overflow Vulnerability

CVE-2024-32318 Overview

CVE-2024-32318 is a stack overflow vulnerability affecting Tenda AC500 V2.0.1.9(1307) firmware. The vulnerability exists in the formSetVlanInfo function, where improper handling of the vlan parameter allows attackers to trigger a stack-based buffer overflow condition. This firmware vulnerability in the Tenda AC500 wireless access controller poses significant risks to network infrastructure security.

Critical Impact

This stack overflow vulnerability enables remote attackers to potentially execute arbitrary code or cause denial of service on affected Tenda AC500 devices without requiring authentication. Exploitation could lead to complete device compromise and network infrastructure takeover.

Affected Products

• Tenda AC500 Firmware V2.0.1.9(1307)
• Tenda AC500 Hardware Devices
• Network environments utilizing Tenda AC500 wireless access controllers

Discovery Timeline

• 2024-04-17 - CVE-2024-32318 published to NVD
• 2025-03-17 - Last updated in NVD database

Technical Details for CVE-2024-32318

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow), a memory corruption issue where data written to a buffer exceeds its allocated size on the stack. The formSetVlanInfo function in the Tenda AC500 firmware fails to properly validate the length of user-supplied input through the vlan parameter before copying it to a fixed-size stack buffer.

When an attacker supplies an oversized value for the vlan parameter, the function writes beyond the boundaries of the allocated stack buffer. This overflow can corrupt adjacent stack memory, including saved return addresses and stack frame pointers. An attacker can leverage this to hijack program execution flow, potentially achieving arbitrary code execution with the privileges of the vulnerable process.

The vulnerability is accessible over the network without requiring any authentication or user interaction, making it particularly dangerous for internet-exposed devices. Successful exploitation could result in complete device compromise, allowing attackers to modify configurations, intercept traffic, or use the device as a pivot point for further network attacks.

Root Cause

The root cause of CVE-2024-32318 is insufficient input validation in the formSetVlanInfo function when processing the vlan parameter. The firmware does not perform adequate bounds checking before copying user-controlled data into a stack-allocated buffer. This lack of proper input sanitization allows maliciously crafted HTTP requests to overflow the buffer and corrupt stack memory.

Attack Vector

The attack vector is network-based, allowing remote exploitation. An attacker can craft a malicious HTTP request to the device's web management interface, providing an oversized vlan parameter value to the formSetVlanInfo endpoint. The attack does not require authentication credentials or user interaction, making it exploitable by any attacker with network access to the vulnerable device.

The exploitation process involves:

1. Identifying a vulnerable Tenda AC500 device on the network
2. Crafting an HTTP request with an oversized vlan parameter
3. Sending the request to trigger the buffer overflow in formSetVlanInfo
4. Overwriting critical stack data to achieve code execution or denial of service

Technical details and proof-of-concept information are available in the GitHub IoT Vulnerability Info repository.

Detection Methods for CVE-2024-32318

Indicators of Compromise

• Unusual HTTP requests to the Tenda AC500 web interface containing abnormally long vlan parameter values
• Device crashes or unexpected reboots of Tenda AC500 access controllers
• Unauthorized configuration changes on network devices
• Network traffic anomalies originating from Tenda AC500 devices

Detection Strategies

• Monitor HTTP traffic to Tenda AC500 devices for requests with oversized parameter values in the formSetVlanInfo endpoint
• Implement intrusion detection rules to flag stack smashing or buffer overflow attack patterns targeting embedded devices
• Deploy network-based anomaly detection to identify unusual request patterns to IoT device management interfaces
• Review device logs for segmentation faults or crash indicators that may suggest exploitation attempts

Monitoring Recommendations

• Isolate Tenda AC500 devices on a dedicated management VLAN with restricted access
• Enable logging on network firewalls for all traffic to and from affected devices
• Implement regular health checks on AC500 devices to detect unexpected behavior or crashes
• Configure alerts for any external access attempts to device management interfaces

How to Mitigate CVE-2024-32318

Immediate Actions Required

• Restrict network access to Tenda AC500 management interfaces to trusted IP addresses only
• Disable remote management features if not required for operational purposes
• Implement network segmentation to isolate vulnerable devices from untrusted networks
• Monitor affected devices for signs of compromise or exploitation attempts
• Consider replacing affected devices if no firmware update is available from the vendor

Patch Information

At the time of publication, no official vendor advisory or firmware patch has been released by Tenda to address CVE-2024-32318. Organizations should monitor Tenda's official support channels for security updates. In the absence of an official patch, implementing the recommended workarounds and network-level mitigations is strongly advised.

Workarounds

• Place Tenda AC500 devices behind a firewall and restrict management interface access to internal networks only
• Use access control lists (ACLs) to limit which hosts can communicate with the device's web interface
• Disable the web management interface if not required and use alternative management methods where available
• Implement a web application firewall (WAF) to filter malicious requests containing oversized parameters

# Example firewall rule to restrict access to device management interface
# Only allow management access from trusted admin subnet

# iptables example - restrict HTTP/HTTPS access to AC500 management
iptables -A FORWARD -d <AC500_IP> -p tcp --dport 80 -s 10.10.10.0/24 -j ACCEPT
iptables -A FORWARD -d <AC500_IP> -p tcp --dport 443 -s 10.10.10.0/24 -j ACCEPT
iptables -A FORWARD -d <AC500_IP> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <AC500_IP> -p tcp --dport 443 -j DROP