CVE-2026-6630: Tenda F451 Buffer Overflow Vulnerability

CVE-2026-6630 Overview

A buffer overflow vulnerability has been identified in the Tenda F451 router firmware version 1.0.0.7_cn_svn7958. The vulnerability exists within the httpd component, specifically in the fromGstDhcpSetSer function located at the /goform/GstDhcpSetSer endpoint. Malicious manipulation of the dips argument can trigger a buffer overflow condition, potentially allowing an attacker to execute arbitrary code or crash the affected device.

Critical Impact

This network-accessible buffer overflow in the Tenda F451 router's web interface could allow remote attackers with low privileges to compromise the device, potentially leading to complete device takeover, network traffic interception, or use of the device as a pivot point for further attacks.

Affected Products

• Tenda F451 firmware version 1.0.0.7_cn_svn7958
• Tenda F451 httpd web server component
• Devices with the /goform/GstDhcpSetSer endpoint exposed

Discovery Timeline

• 2026-04-20 - CVE-2026-6630 published to NVD
• 2026-04-22 - Last updated in NVD database

Technical Details for CVE-2026-6630

Vulnerability Analysis

This vulnerability is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The fromGstDhcpSetSer function in the Tenda F451's httpd service fails to properly validate the length of input provided through the dips parameter before copying it into a fixed-size buffer. When an attacker supplies an overly long input value, the data overflows the allocated buffer boundary, corrupting adjacent memory regions.

The vulnerability is remotely exploitable over the network and requires only low-level privileges to trigger. No user interaction is required for successful exploitation. Successful exploitation could result in complete compromise of the device's confidentiality, integrity, and availability. An exploit for this vulnerability has been publicly disclosed, increasing the risk of active exploitation.

Root Cause

The root cause of this vulnerability lies in insufficient input validation and bounds checking within the fromGstDhcpSetSer function. When processing HTTP requests to the /goform/GstDhcpSetSer endpoint, the function accepts the dips argument without verifying that its length does not exceed the size of the destination buffer. This classic buffer overflow pattern allows memory beyond the intended buffer to be overwritten with attacker-controlled data.

Attack Vector

The attack can be initiated remotely over the network by sending a specially crafted HTTP request to the vulnerable endpoint. An attacker would target the /goform/GstDhcpSetSer endpoint on the Tenda F451's web management interface, providing a maliciously crafted dips parameter value designed to overflow the target buffer.

The exploitation mechanism involves sending an HTTP POST request containing an oversized dips parameter value. When the fromGstDhcpSetSer function processes this input without proper bounds checking, the buffer overflow occurs. Depending on the memory layout and exploitation technique, this could allow an attacker to overwrite return addresses, function pointers, or other critical data structures to achieve code execution or cause a denial of service. For detailed technical information, refer to the GitHub issue tracker entry and VulDB vulnerability details.

Detection Methods for CVE-2026-6630

Indicators of Compromise

• Unexpected HTTP POST requests to /goform/GstDhcpSetSer endpoint with abnormally large dips parameter values
• Router crashes, reboots, or unresponsive web management interfaces following suspicious HTTP requests
• Unusual network traffic patterns originating from or destined to Tenda F451 devices
• Evidence of unauthorized configuration changes on affected routers

Detection Strategies

• Implement network intrusion detection rules to monitor for HTTP requests targeting /goform/GstDhcpSetSer with large payload sizes
• Deploy web application firewall (WAF) rules to block requests with oversized parameters to Tenda router management interfaces
• Monitor device logs for repeated crashes or unexpected restarts of the httpd service
• Use SentinelOne Singularity for IoT/network device monitoring to detect anomalous behavior patterns

Monitoring Recommendations

• Enable comprehensive logging on network perimeter devices to capture traffic to and from Tenda routers
• Implement alerting for any access attempts to router management interfaces from untrusted network segments
• Regularly audit network traffic for reconnaissance attempts targeting Tenda device management ports
• Deploy network segmentation to isolate IoT and network infrastructure devices from general network traffic

How to Mitigate CVE-2026-6630

Immediate Actions Required

• Restrict access to the Tenda F451 web management interface to trusted internal networks only using firewall rules
• Disable remote management access if not strictly required for operations
• Implement network segmentation to isolate affected devices from untrusted network segments
• Monitor the Tenda security page for firmware updates addressing this vulnerability

Patch Information

At the time of publication, no official patch has been confirmed from Tenda for this vulnerability. Organizations should monitor the Tenda official website for security advisories and firmware updates. Consider replacing affected devices with alternative hardware if a patch is not released in a timely manner. Additional technical details are available through VulDB.

Workarounds

• Implement strict access control lists (ACLs) to limit management interface access to authorized IP addresses only
• Deploy a network firewall or reverse proxy in front of the device to filter and validate incoming HTTP requests
• Disable the web management interface entirely if alternative management methods (such as console access) are available
• Consider network isolation or replacing vulnerable devices with supported alternatives until a patch is available

# Example firewall rule to restrict access to Tenda management interface (iptables)
# Replace 192.168.1.0/24 with your trusted management network
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP