CVE-2024-30635: Tenda F1202 Buffer Overflow Vulnerability

CVE-2024-30635 Overview

CVE-2024-30635 is a stack overflow vulnerability affecting Tenda F1202 routers running firmware version 1.2.0.20(408). The vulnerability exists in the funcpara1 parameter within the formSetCfm function, allowing remote attackers to potentially execute arbitrary code or cause denial of service on affected devices without requiring authentication.

Critical Impact

This stack overflow vulnerability in Tenda F1202 routers can be exploited remotely without authentication, potentially allowing attackers to gain complete control of the device or disrupt network connectivity.

Affected Products

• Tenda F1202 Firmware version 1.2.0.20(408)
• Tenda F1202 Hardware

Discovery Timeline

• 2024-03-29 - CVE-2024-30635 published to NVD
• 2025-03-13 - Last updated in NVD database

Technical Details for CVE-2024-30635

Vulnerability Analysis

This vulnerability is classified as CWE-120 (Buffer Copy without Checking Size of Input), commonly known as a classic buffer overflow. The formSetCfm function in the Tenda F1202 firmware fails to properly validate the length of user-supplied data passed through the funcpara1 parameter before copying it to a stack buffer. This lack of bounds checking allows an attacker to write beyond the allocated buffer space on the stack, potentially overwriting critical program data such as return addresses or function pointers.

The network-accessible nature of this vulnerability means that attackers can exploit it remotely without any prior authentication or user interaction. Combined with the firmware's likely lack of modern memory protection mechanisms common in embedded devices, successful exploitation could result in complete device compromise.

Root Cause

The root cause lies in improper input validation within the formSetCfm function. When processing the funcpara1 parameter, the function copies user-supplied data into a fixed-size stack buffer without first verifying that the input length does not exceed the buffer's capacity. This classic buffer overflow pattern (CWE-120) is particularly common in embedded device firmware where memory-safe programming practices may not be consistently applied.

Attack Vector

The attack vector is network-based, meaning an attacker can craft malicious HTTP requests targeting the formSetCfm function endpoint on the router's web interface. By supplying an oversized value for the funcpara1 parameter, the attacker can trigger the stack overflow condition.

The exploitation flow typically involves:

1. Identifying a vulnerable Tenda F1202 router on the network
2. Crafting a malicious HTTP request with an oversized funcpara1 parameter
3. Sending the request to the router's web management interface
4. Overwriting the stack to control program execution or cause a crash

For detailed technical documentation of this vulnerability, refer to the GitHub Vulnerability Documentation.

Detection Methods for CVE-2024-30635

Indicators of Compromise

• Unexpected router reboots or crashes indicating potential exploitation attempts
• Anomalous HTTP requests to the router's web interface with unusually large parameter values
• Modified router configuration settings without administrator action
• Unfamiliar outbound network connections from the router
• Degraded network performance or connectivity issues

Detection Strategies

• Monitor HTTP traffic to the router management interface for requests with abnormally large funcpara1 parameters
• Implement network-based intrusion detection rules to identify buffer overflow attack patterns targeting Tenda devices
• Review router access logs for suspicious requests to the formSetCfm endpoint
• Deploy network segmentation to isolate IoT devices and monitor cross-segment traffic

Monitoring Recommendations

• Enable logging on the Tenda F1202 router if supported and regularly review logs for suspicious activity
• Monitor network traffic for unexpected connections originating from the router
• Implement network monitoring solutions to detect anomalous traffic patterns to/from IoT devices
• Set up alerts for any configuration changes or administrative actions on the router

How to Mitigate CVE-2024-30635

Immediate Actions Required

• Restrict access to the router's web management interface to trusted internal networks only
• Disable remote management features if enabled
• Place the router behind a firewall and block external access to administrative ports
• Monitor for any available firmware updates from Tenda that address this vulnerability
• Consider replacing affected devices with alternatives that have better security support

Patch Information

At the time of publication, no official patch information has been released by Tenda for this vulnerability. Organizations should monitor Tenda's official support channels for firmware updates that address CVE-2024-30635. Given the critical severity and lack of available patches, implementing network-level mitigations is essential.

Workarounds

• Disable the web management interface entirely if not required for operations
• Implement strict network access controls to limit which hosts can reach the router's management interface
• Use a VPN or jump host to access the router management interface rather than exposing it directly
• Segment the network to isolate the affected router from critical systems
• Consider deploying a firewall rule to filter requests with oversized parameters destined for the router

# Example iptables rule to restrict access to router management interface
# Replace 192.168.1.1 with your router's IP and adjust the allowed source network
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP