CVE-2024-0923: Tenda AC10U Buffer Overflow Vulnerability

CVE-2024-0923 Overview

A critical stack-based buffer overflow vulnerability has been identified in the Tenda AC10U router firmware version 15.03.06.49_multi_TDE01. The vulnerability exists in the formSetDeviceName function, where improper handling of the devName argument allows an attacker to trigger a stack-based buffer overflow condition. This vulnerability can be exploited remotely without authentication, potentially enabling complete device compromise.

Critical Impact

This vulnerability allows remote attackers to execute arbitrary code on affected Tenda AC10U routers without authentication, potentially leading to complete device takeover, network infiltration, and use of compromised devices in botnet operations.

Affected Products

• Tenda AC10U Firmware version 15.03.06.49_multi_TDE01
• Tenda AC10U Hardware version 1.0
• All Tenda AC10U devices running the affected firmware version

Discovery Timeline

• 2024-01-26 - CVE-2024-0923 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-0923

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow). The formSetDeviceName function in the Tenda AC10U firmware fails to properly validate the length of user-supplied input provided through the devName parameter. When an attacker provides an overly long device name, the function copies this data into a fixed-size stack buffer without performing adequate bounds checking.

The exploitation of this vulnerability does not require authentication, and the attack can be launched remotely over the network. The vulnerable function is accessible through the router's web management interface, making it a prime target for remote attackers seeking to compromise consumer networking equipment.

Root Cause

The root cause of this vulnerability is the absence of proper input validation and boundary checks in the formSetDeviceName function. The function allocates a fixed-size buffer on the stack to hold the device name but does not verify that the incoming devName parameter fits within this allocated space before copying the data. This classic programming error allows attackers to overflow the stack buffer, overwrite adjacent memory including return addresses, and potentially hijack the execution flow of the device.

Attack Vector

The attack can be launched remotely over the network against the router's web management interface. An attacker crafts a malicious HTTP request containing an oversized devName parameter and sends it to the vulnerable formSetDeviceName endpoint. The vulnerability requires no authentication (PR:N) and no user interaction (UI:N), making it trivially exploitable by anyone with network access to the device's management interface.

The exploitation process involves:

1. Identifying a vulnerable Tenda AC10U device on the network
2. Crafting a specially designed HTTP request with an oversized devName parameter
3. Sending the request to the formSetDeviceName endpoint
4. Overflowing the stack buffer to overwrite the return address
5. Redirecting execution to attacker-controlled shellcode

The vulnerability has been publicly disclosed with technical details available in the GitHub advisory. Detailed tracking information is also available through VulDB #252128.

Detection Methods for CVE-2024-0923

Indicators of Compromise

• Unusual HTTP requests to the router's web interface containing abnormally long devName parameters
• Unexpected device reboots or crashes indicating potential exploitation attempts
• Modified device configurations or unexpected device name changes
• Anomalous outbound network connections from the router to unknown IP addresses
• Presence of unknown processes or services running on the device

Detection Strategies

• Monitor HTTP traffic to the router's management interface for requests containing oversized parameters targeting the formSetDeviceName function
• Deploy network intrusion detection rules to identify buffer overflow attack patterns against Tenda devices
• Implement web application firewall rules to block requests with excessively long parameter values
• Use SentinelOne Singularity to detect anomalous behavior patterns indicative of firmware-level compromise

Monitoring Recommendations

• Enable logging on network perimeter devices to capture all traffic to and from IoT devices
• Implement network segmentation to isolate IoT devices and limit lateral movement potential
• Regularly audit network traffic patterns from router devices for signs of command and control communications
• Configure alerts for any configuration changes or firmware modifications on network devices

How to Mitigate CVE-2024-0923

Immediate Actions Required

• Restrict network access to the router's web management interface to trusted IP addresses only
• Disable remote management features if not required for operations
• Implement network segmentation to isolate the vulnerable device from critical network resources
• Monitor for exploitation attempts using network intrusion detection systems
• Consider replacing vulnerable devices if no patch becomes available

Patch Information

No official patch has been released by the vendor at this time. According to the vulnerability disclosure, the vendor (Tenda) was contacted early about this issue but did not respond. Organizations using affected devices should implement compensating controls until a firmware update is made available.

For the latest information, consult:

• VulDB Advisory
• Technical Analysis on GitHub

Workarounds

• Disable the web management interface if not actively needed for device administration
• Use firewall rules to block external access to the router's management ports (typically 80/443)
• Implement MAC address filtering to restrict which devices can access the management interface
• Deploy an upstream firewall or IPS to filter malicious requests before they reach the vulnerable device

# Example iptables rules to restrict management interface access
# Block external access to management ports
iptables -A INPUT -p tcp --dport 80 -i eth0 -j DROP
iptables -A INPUT -p tcp --dport 443 -i eth0 -j DROP

# Allow management access only from trusted internal IP
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.100 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.100 -j ACCEPT