CVE-2024-2852: Tenda AC15 Buffer Overflow Vulnerability

CVE-2024-2852 Overview

A critical stack-based buffer overflow vulnerability has been discovered in the Tenda AC15 router firmware version 15.03.20_multi. This vulnerability exists within the saveParentControlInfo function located in the /goform/saveParentControlInfo endpoint. An attacker can exploit this flaw by manipulating the urls argument, leading to a stack-based buffer overflow condition that can be triggered remotely without authentication.

The exploit for this vulnerability has been publicly disclosed, and despite early contact with the vendor regarding responsible disclosure, Tenda did not respond. This lack of vendor response leaves affected devices potentially unpatched and vulnerable to exploitation.

Critical Impact

Remote attackers can exploit this stack-based buffer overflow to execute arbitrary code, potentially gaining complete control over the affected Tenda AC15 router without any authentication requirements.

Affected Products

• Tenda AC15 Firmware version 15.03.20_multi
• Tenda AC15 Hardware version 1.0

Discovery Timeline

• 2024-03-24 - CVE-2024-2852 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-2852

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow), a memory corruption flaw that occurs when the saveParentControlInfo function fails to properly validate the length of user-supplied input through the urls parameter. The function processes HTTP requests at the /goform/saveParentControlInfo endpoint without adequate bounds checking, allowing attackers to write beyond the allocated stack buffer.

Stack-based buffer overflows in embedded device firmware are particularly dangerous as they often execute with elevated privileges and may allow attackers to overwrite critical stack data including return addresses, potentially redirecting program execution to attacker-controlled code.

Root Cause

The root cause of this vulnerability lies in improper input validation within the saveParentControlInfo function. When processing the urls argument from incoming HTTP requests, the function copies user-supplied data to a fixed-size stack buffer without verifying that the input length does not exceed the buffer's capacity. This allows an attacker to supply an oversized urls value that overflows the stack buffer, corrupting adjacent memory and potentially hijacking program control flow.

Attack Vector

This vulnerability can be exploited remotely over the network. An attacker sends a specially crafted HTTP request to the /goform/saveParentControlInfo endpoint with a malicious urls parameter containing data designed to overflow the stack buffer. The attack requires no authentication or user interaction, making it highly accessible to remote attackers who can reach the router's web interface.

The exploitation mechanism involves:

1. Sending an HTTP POST request to /goform/saveParentControlInfo
2. Including an oversized urls parameter value
3. The overflow corrupts stack memory, potentially overwriting the return address
4. Attacker-controlled code execution may be achieved upon function return

Technical details of the vulnerability can be found in the GitHub vulnerability documentation.

Detection Methods for CVE-2024-2852

Indicators of Compromise

• Unusual HTTP POST requests targeting /goform/saveParentControlInfo with abnormally large payloads
• Router instability, unexpected reboots, or crashes following HTTP requests
• Anomalous network traffic patterns originating from the router's management interface
• Unexpected processes or services running on the router device

Detection Strategies

• Implement network monitoring to detect HTTP requests to /goform/saveParentControlInfo containing oversized urls parameters
• Deploy intrusion detection signatures to identify buffer overflow exploitation attempts against Tenda AC15 devices
• Monitor for unusual outbound connections from router devices that may indicate post-exploitation activity
• Enable logging on upstream firewalls to capture requests to vulnerable endpoints

Monitoring Recommendations

• Restrict access to the router's web management interface to trusted internal networks only
• Implement network segmentation to isolate IoT devices including routers from critical network segments
• Deploy network-based anomaly detection to identify exploitation attempts and post-compromise activity
• Regularly review device logs for signs of unauthorized access attempts

How to Mitigate CVE-2024-2852

Immediate Actions Required

• Disable remote management access to the Tenda AC15 router immediately
• Restrict access to the router's web interface using firewall rules, limiting connectivity to trusted administrator IP addresses only
• Place the affected router behind a properly configured firewall that blocks external access to management interfaces
• Consider replacing the vulnerable device with a supported alternative if no patch becomes available

Patch Information

As of the last update, Tenda has not responded to disclosure attempts and no official patch is available for this vulnerability. The vendor was contacted early about this disclosure but did not respond in any way. Users should monitor the VulDB entry and Tenda's official channels for any future security updates.

Workarounds

• Disable the router's remote management interface to prevent external exploitation
• Implement strict firewall rules to block all external access to the device's web management ports
• Use a VPN for remote administration needs rather than exposing the management interface directly
• Consider network segmentation to limit the potential impact of a compromised router

# Example firewall rule to restrict access to router management interface
# Block external access to router web interface (adjust IP addresses as needed)
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP