CVE-2024-0929: Tenda AC10U Buffer Overflow Vulnerability

CVE-2024-0929 Overview

A critical stack-based buffer overflow vulnerability has been identified in the Tenda AC10U wireless router firmware version 15.03.06.49_multi_TDE01. This vulnerability exists within the fromNatStaticSetting function, where improper handling of the page argument allows attackers to trigger a buffer overflow condition. The flaw can be exploited remotely without authentication, potentially allowing complete compromise of the affected device.

Critical Impact

Remote attackers can exploit this vulnerability to execute arbitrary code on affected Tenda AC10U routers, potentially gaining full control of the device and enabling lateral movement within the network. The exploit has been publicly disclosed.

Affected Products

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

Discovery Timeline

• 2024-01-26 - CVE-2024-0929 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-0929

Vulnerability Analysis

This firmware vulnerability affects the NAT static setting functionality within the Tenda AC10U router's web management interface. The fromNatStaticSetting function fails to properly validate the length of user-supplied input in the page parameter before copying it to a fixed-size stack buffer. When an attacker provides an overly long value for this parameter, the data overflows the allocated buffer space on the stack, overwriting adjacent memory including saved return addresses and other critical control data.

The vulnerability is particularly dangerous because it can be triggered remotely over the network without requiring any authentication. An attacker with network access to the router's management interface can craft malicious HTTP requests containing an oversized page parameter value to trigger the overflow condition.

Root Cause

The root cause of this vulnerability is the absence of proper bounds checking in the fromNatStaticSetting function when processing the page argument. The function uses an unsafe string copy operation that does not verify whether the input data fits within the destination buffer's allocated size. This classic CWE-121 (Stack-based Buffer Overflow) pattern allows attackers to corrupt stack memory and potentially hijack program execution flow.

Attack Vector

The attack vector is network-based, requiring the attacker to send specially crafted HTTP requests to the router's web management interface. The exploitation process involves manipulating the page parameter within requests handled by the fromNatStaticSetting function. Due to the nature of stack-based buffer overflows on embedded systems, successful exploitation could allow the attacker to overwrite the return address and redirect execution to attacker-controlled shellcode.

Technical details and additional documentation regarding this vulnerability can be found in the GitHub IoT Documentation and the VulDB entry #252134.

Detection Methods for CVE-2024-0929

Indicators of Compromise

• Unusual HTTP requests to the router's web management interface containing abnormally long page parameter values
• Unexpected router reboots or crashes that may indicate exploitation attempts
• Anomalous network traffic originating from the router to external command and control servers
• Changes to router configuration or firmware that were not authorized by administrators

Detection Strategies

• Implement network intrusion detection rules to identify HTTP requests with oversized parameters targeting Tenda router management interfaces
• Monitor router logs for repeated authentication failures or unusual access patterns to the NAT configuration endpoints
• Deploy network traffic analysis to detect buffer overflow attack signatures in HTTP POST requests
• Use firmware integrity verification to detect unauthorized modifications following a potential compromise

Monitoring Recommendations

• Restrict access to the router's web management interface to trusted internal networks only
• Enable logging on network perimeter devices to capture traffic destined for router management ports
• Implement alerting for any access attempts to the router management interface from untrusted networks
• Regularly audit connected devices for signs of compromise or unusual behavior

How to Mitigate CVE-2024-0929

Immediate Actions Required

• Restrict network access to the router's web management interface using firewall rules or access control lists
• Disable remote management features if not required for operations
• Isolate affected Tenda AC10U devices from critical network segments
• Consider replacing vulnerable devices with alternative hardware if no vendor patch is available

Patch Information

The vendor (Tenda) was contacted about this vulnerability but did not respond. As of the last update on 2024-11-21, no official patch has been released by the vendor. Organizations using affected devices should implement the workarounds described below and consider device replacement as a long-term mitigation strategy.

Workarounds

• Disable the web management interface entirely if remote administration is not required
• Implement strict firewall rules to allow management access only from specific trusted IP addresses
• Place the router behind an additional security appliance that can filter malicious requests
• Use a VPN for remote management instead of exposing the management interface directly

# Example: Restrict management access via iptables on upstream firewall
iptables -A FORWARD -d <router_ip> -p tcp --dport 80 -j DROP
iptables -A FORWARD -s <trusted_admin_ip> -d <router_ip> -p tcp --dport 80 -j ACCEPT