CVE-2024-0925: Tenda AC10U Buffer Overflow Vulnerability

CVE-2024-0925 Overview

A critical stack-based buffer overflow vulnerability has been discovered in the Tenda AC10U wireless router firmware version 15.03.06.49_multi_TDE01. This vulnerability affects the formSetVirtualSer function, where improper handling of the list argument allows attackers to overflow the stack buffer, potentially leading to remote code execution on affected devices.

The vulnerability can be exploited remotely without authentication, making it particularly dangerous for consumer and small business network deployments. The exploit has been publicly disclosed, increasing the risk of active exploitation in the wild. Notably, the vendor was contacted about this disclosure but did not respond, leaving affected devices without an official patch.

Critical Impact

Remote attackers can exploit this stack-based buffer overflow to execute arbitrary code on Tenda AC10U routers, potentially gaining complete control over the device and using it as a pivot point for further network intrusion.

Affected Products

• Tenda AC10U Firmware version 15.03.06.49_multi_TDE01
• Tenda AC10U Hardware version 1.0
• Tendacn AC10U wireless router devices

Discovery Timeline

• 2024-01-26 - CVE-2024-0925 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-0925

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow), a memory corruption flaw that occurs when data written to a buffer on the stack exceeds its allocated size, overwriting adjacent memory including return addresses and saved registers.

The vulnerable function formSetVirtualSer processes user-supplied input through the list parameter without adequate bounds checking. When an attacker provides an oversized input value, the function copies this data into a fixed-size stack buffer, causing an overflow condition. This overflow can corrupt the function's return address, allowing the attacker to redirect execution flow to malicious code.

The network-accessible nature of this vulnerability is particularly concerning for IoT devices like wireless routers, which are often exposed directly to the internet or positioned at network perimeters. Successful exploitation could allow attackers to install persistent backdoors, intercept network traffic, or use the compromised router as part of a botnet infrastructure.

Root Cause

The root cause is insufficient input validation in the formSetVirtualSer function when processing the list argument. The function allocates a fixed-size buffer on the stack but fails to verify that the incoming data fits within this buffer before performing copy operations. This classic buffer overflow condition allows attackers to write beyond the buffer boundaries, corrupting stack memory and potentially hijacking program execution.

Attack Vector

The attack vector is network-based, requiring no authentication or user interaction. An attacker can craft a malicious HTTP request to the router's web management interface, targeting the vulnerable formSetVirtualSer endpoint with an oversized list parameter. The attack can be initiated remotely from anywhere on the network segment that has access to the router's management interface, or from the internet if the management interface is externally accessible.

The attack exploits the formSetVirtualSer function by supplying a crafted list parameter value that exceeds the expected buffer size. When the function processes this input, the overflow corrupts stack memory, allowing the attacker to control the execution flow. For detailed technical analysis and proof-of-concept information, see the GitHub PoC Documentation and VulDB analysis.

Detection Methods for CVE-2024-0925

Indicators of Compromise

• Unusual HTTP POST requests to the router's web interface containing abnormally long list parameter values targeting formSetVirtualSer
• Router crashes, unexpected reboots, or unresponsive management interfaces
• Unexpected outbound network connections from the router to unknown IP addresses
• Changes to router configuration or firmware without administrator action

Detection Strategies

• Monitor HTTP traffic to router management interfaces for requests with oversized parameters or unusual payload patterns
• Implement network intrusion detection rules to identify buffer overflow exploitation attempts targeting Tenda devices
• Enable logging on network segments containing vulnerable routers and alert on anomalous traffic patterns
• Deploy SentinelOne Singularity to detect and prevent exploitation attempts through behavioral analysis and memory protection

Monitoring Recommendations

• Regularly audit router firmware versions and maintain an inventory of Tenda AC10U devices running vulnerable firmware
• Monitor network traffic patterns for signs of compromised routers acting as command-and-control nodes
• Implement network segmentation to isolate IoT devices and limit lateral movement capabilities
• Review router access logs for failed authentication attempts or suspicious administrative actions

How to Mitigate CVE-2024-0925

Immediate Actions Required

• Restrict access to the router's web management interface to trusted internal networks only
• Disable remote management features if not required for operations
• Implement firewall rules to block external access to the router's administrative ports
• Consider replacing affected devices with alternative hardware from vendors with active security response programs

Patch Information

No official patch is currently available from Tenda. The vendor was contacted early about this disclosure but did not respond. Users should monitor Tenda's official website for any future firmware updates that may address this vulnerability.

In the absence of a vendor patch, organizations should implement network-level mitigations and consider device replacement with actively supported alternatives. For additional vulnerability details, refer to VulDB #252130.

Workarounds

• Configure firewall rules to restrict management interface access to specific trusted IP addresses only
• Place affected routers behind a VPN, requiring authentication before management interface access
• Disable the web management interface entirely if command-line management is available and sufficient
• Implement network monitoring to detect and alert on potential exploitation attempts

# Example firewall rules to restrict management access (apply on upstream firewall)
# Block external access to router management port
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 443 -j DROP

# Allow only specific trusted management IPs
iptables -I FORWARD -s <TRUSTED_ADMIN_IP> -d <ROUTER_IP> -p tcp --dport 80 -j ACCEPT