CVE-2024-2850: Tenda AC15 Buffer Overflow Vulnerability

CVE-2024-2850 Overview

A critical stack-based buffer overflow vulnerability has been identified in the Tenda AC15 router firmware version 15.03.05.18. The vulnerability exists in the saveParentControlInfo function located in the /goform/saveParentControlInfo endpoint. Improper handling of the urls parameter allows an unauthenticated remote attacker to trigger a stack-based buffer overflow, potentially leading to complete device compromise.

Critical Impact

Remote attackers can exploit this vulnerability without authentication to execute arbitrary code, potentially gaining full control of the affected Tenda AC15 router and compromising network security.

Affected Products

• Tenda AC15 Firmware version 15.03.05.18
• Tenda AC15 hardware device

Discovery Timeline

• 2024-03-24 - CVE-2024-2850 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-2850

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow), a memory corruption issue that occurs when a program writes data beyond the boundaries of a fixed-size stack buffer. In the context of the Tenda AC15 router, the saveParentControlInfo function fails to properly validate the length of user-supplied input in the urls parameter before copying it to a stack buffer.

The vulnerability is exploitable remotely over the network without requiring any authentication or user interaction. Successful exploitation allows an attacker to overwrite critical stack data including the return address, enabling arbitrary code execution with the privileges of the web service running on the router.

Root Cause

The root cause of this vulnerability is insufficient bounds checking in the saveParentControlInfo function when processing the urls parameter. The function accepts HTTP POST requests at the /goform/saveParentControlInfo endpoint and copies the user-controlled urls data into a fixed-size stack buffer without verifying that the input length does not exceed the buffer capacity. This classic buffer overflow condition allows attackers to corrupt adjacent stack memory.

Attack Vector

The attack can be launched remotely over the network against the router's web management interface. An attacker crafts a malicious HTTP POST request to /goform/saveParentControlInfo with an oversized urls parameter. When the vulnerable function processes this input, the stack buffer is overflowed, overwriting the saved return address on the stack.

The vulnerability is particularly dangerous because it requires no authentication, meaning any attacker with network access to the router's management interface can attempt exploitation. The urls parameter manipulation allows precise control over the data written to the stack, facilitating reliable exploitation.

For detailed technical analysis and proof-of-concept information, see the GitHub IoT Vulnerability Report.

Detection Methods for CVE-2024-2850

Indicators of Compromise

• Abnormal HTTP POST requests to /goform/saveParentControlInfo with unusually large urls parameter values
• Router crashes or unexpected reboots that may indicate failed exploitation attempts
• Unexpected network traffic originating from the router to external hosts
• Modified router configuration or firmware that was not authorized by administrators

Detection Strategies

• Monitor HTTP traffic to the router's web management interface for POST requests to /goform/saveParentControlInfo containing oversized payloads
• Implement network-based intrusion detection rules to flag suspicious patterns in requests to Tenda router endpoints
• Deploy SentinelOne Singularity for network visibility to detect exploitation attempts targeting IoT devices
• Analyze router logs for repeated crashes or authentication failures that may indicate attack activity

Monitoring Recommendations

• Enable logging on the router if available and forward logs to a central SIEM for analysis
• Segment IoT devices including routers on dedicated network VLANs with strict traffic monitoring
• Implement continuous vulnerability scanning to identify unpatched Tenda devices in your environment
• Monitor for firmware integrity changes that could indicate successful compromise

How to Mitigate CVE-2024-2850

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only
• Disable remote management access from the WAN interface if not required
• Place the Tenda AC15 router behind a firewall that blocks unauthorized access to management ports
• Consider replacing the affected device with a router from a vendor that provides timely security updates
• Monitor the device for signs of compromise while awaiting vendor response

Patch Information

No official patch is currently available from Tenda. According to the vulnerability disclosure, the vendor was contacted early about this issue but did not respond. Users should check VulDB #257774 for updates on vendor response and potential patches. Given the lack of vendor engagement, affected organizations should strongly consider device replacement with products from vendors with demonstrated security response capabilities.

Workarounds

• Implement network access control lists (ACLs) to restrict management interface access to specific administrator IP addresses
• Use a VPN for remote administration instead of exposing the web interface directly
• Disable the web management interface entirely if device configuration can be managed through other means
• Deploy network segmentation to isolate the vulnerable router from critical network segments

# Example: Restrict management access via upstream firewall (iptables)
# 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 trusted admin subnet
iptables -I FORWARD -s <ADMIN_SUBNET> -d <ROUTER_IP> -p tcp --dport 80 -j ACCEPT