CVE-2024-0926: Tenda AC10U Buffer Overflow Vulnerability

CVE-2024-0926 Overview

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

Critical Impact

This stack-based buffer overflow in the Tenda AC10U router can be exploited remotely to achieve complete system compromise, affecting confidentiality, integrity, and availability of the device.

Affected Products

• Tenda AC10U Firmware version 15.03.06.49_multi_TDE01
• Tenda AC10U Hardware version 1.0

Discovery Timeline

• 2024-01-26 - CVE-2024-0926 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-0926

Vulnerability Analysis

This vulnerability resides within the formWifiWpsOOB function of the Tenda AC10U router firmware. The function fails to properly validate the bounds of the index argument before processing it, leading to a classic stack-based buffer overflow condition (CWE-121).

The network-accessible nature of this vulnerability means attackers can exploit it remotely without requiring any user interaction or prior authentication. When successfully exploited, an attacker gains the ability to overwrite critical memory regions on the stack, potentially hijacking program execution flow and achieving arbitrary code execution with the privileges of the affected process.

The exploit has been publicly disclosed, and a proof-of-concept is available in public repositories. The vendor (Tenda) was contacted early about this disclosure but did not respond in any way, leaving users without an official patch.

Root Cause

The root cause is a failure to perform adequate bounds checking on the index parameter within the formWifiWpsOOB function. When user-controlled input is passed to this function without proper validation, it can overflow the allocated stack buffer, corrupting adjacent memory including return addresses and saved registers.

This is a common vulnerability pattern in embedded device firmware where memory safety measures are often minimal or absent due to resource constraints, and input validation is inconsistent across different code paths.

Attack Vector

The attack can be initiated remotely over the network against the router's web management interface. An attacker does not need authentication or any form of user interaction to exploit this vulnerability.

The attack flow involves:

1. The attacker identifies a vulnerable Tenda AC10U router accessible on the network
2. A specially crafted request is sent to the web interface targeting the formWifiWpsOOB function
3. The malicious index parameter value overflows the stack buffer
4. Stack memory is corrupted, potentially including the return address
5. The attacker gains control of execution flow, enabling arbitrary code execution

For detailed technical analysis and proof-of-concept information, refer to the GitHub PoC Repository and the VulDB advisory.

Detection Methods for CVE-2024-0926

Indicators of Compromise

• Unexpected requests to the router's web management interface targeting WPS-related endpoints
• Abnormal patterns in the index parameter with unusually long or malformed values
• Router crashes, reboots, or unresponsive behavior following web interface access
• Unauthorized configuration changes or new administrative accounts on the device

Detection Strategies

• Deploy network intrusion detection systems (NIDS) to monitor traffic to Tenda AC10U management interfaces
• Implement web application firewall rules to detect and block requests with abnormally long parameter values targeting known vulnerable endpoints
• Monitor router logs for repeated access attempts to WPS configuration endpoints
• Use SentinelOne Singularity to detect anomalous network behavior indicative of exploitation attempts against IoT devices

Monitoring Recommendations

• Enable logging on the router's web management interface and forward logs to a centralized SIEM
• Restrict access to the router's management interface to trusted networks or IP addresses only
• Implement network segmentation to isolate IoT devices from critical infrastructure
• Regularly audit network traffic for suspicious patterns targeting embedded devices

How to Mitigate CVE-2024-0926

Immediate Actions Required

• Disable remote management access to the Tenda AC10U router immediately
• Restrict access to the router's web interface to local, trusted networks only
• Implement firewall rules to block untrusted access to the device's management ports
• Consider replacing the affected device with a supported product that receives security updates

Patch Information

No official patch is currently available from the vendor. According to the vulnerability disclosure, Tenda was contacted early about this issue but did not respond. Users should contact Tenda support directly for any potential firmware updates and monitor the vendor's website for security advisories.

Given the lack of vendor response, organizations should consider the following alternatives:

• Replace vulnerable devices with actively maintained alternatives
• Implement compensating controls as described in the workarounds section
• Monitor community resources for any unofficial patches or mitigations

Workarounds

• Disable the WPS functionality on the router if not required
• Place the router behind a properly configured firewall that blocks external access to management interfaces
• Use network access control lists (ACLs) to restrict management interface access to specific trusted IP addresses
• Enable HTTPS-only access to the management interface and disable HTTP
• Consider deploying a VPN to access the router's management interface remotely instead of exposing it directly

# Recommended firewall rules to restrict management access (example using iptables)
# Block external access to common router management ports
iptables -A INPUT -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -p tcp --dport 8080 -s ! 192.168.1.0/24 -j DROP