CVE-2026-6632: Tenda F451 Buffer Overflow Vulnerability

CVE-2026-6632 Overview

A buffer overflow vulnerability has been identified in the Tenda F451 router firmware version 1.0.0.7_cn_svn7958. The vulnerability exists in the fromSafeClientFilter function within the /goform/SafeClientFilter endpoint of the httpd component. Remote attackers can exploit this vulnerability by manipulating the menufacturer or Go arguments to cause a buffer overflow condition, potentially leading to arbitrary code execution or denial of service on the affected device.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability over the network to potentially execute arbitrary code on vulnerable Tenda F451 routers, compromising network infrastructure security.

Affected Products

• Tenda F451 Firmware version 1.0.0.7_cn_svn7958

Discovery Timeline

• 2026-04-20 - CVE-2026-6632 published to NVD
• 2026-04-22 - Last updated in NVD database

Technical Details for CVE-2026-6632

Vulnerability Analysis

This vulnerability is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw exists in how the fromSafeClientFilter function processes user-supplied input through the httpd web server component. When handling requests to the /goform/SafeClientFilter endpoint, the function fails to properly validate the length of data supplied via the menufacturer and Go parameters before copying it into a fixed-size buffer.

The network-accessible nature of this vulnerability makes it particularly concerning for devices deployed in edge network positions. Successful exploitation could allow an authenticated attacker to execute arbitrary code with the privileges of the web server process, potentially leading to complete device compromise.

Root Cause

The root cause of this vulnerability is improper bounds checking in the fromSafeClientFilter function. The function accepts user input from HTTP POST parameters without adequately validating the input length against the destination buffer capacity. This classic buffer overflow scenario occurs when oversized input data overwrites adjacent memory locations, potentially corrupting control flow data structures such as return addresses or function pointers.

Attack Vector

The attack can be executed remotely over the network by sending a crafted HTTP request to the vulnerable /goform/SafeClientFilter endpoint. The attacker must have low-privilege authentication to access this endpoint. By supplying an oversized value in the menufacturer or Go parameters, the attacker can overflow the buffer and potentially:

1. Cause a denial of service by crashing the httpd process
2. Overwrite critical memory structures to redirect program execution
3. Execute arbitrary shellcode injected as part of the overflow payload

The vulnerability manifests in the HTTP request handling routines of the Tenda F451's web management interface. For detailed technical analysis and proof-of-concept information, refer to the GitHub Issue Discussion and VulDB entry.

Detection Methods for CVE-2026-6632

Indicators of Compromise

• Unusual HTTP POST requests to /goform/SafeClientFilter with abnormally large parameter values
• Unexpected crashes or restarts of the httpd service on Tenda F451 devices
• Suspicious network traffic patterns targeting the router's web management interface
• Evidence of unauthorized configuration changes on the device

Detection Strategies

• Monitor network traffic for HTTP requests to /goform/SafeClientFilter containing unusually long menufacturer or Go parameter values
• Implement intrusion detection rules to flag requests exceeding expected parameter lengths for the affected endpoint
• Review web server logs on Tenda F451 devices for patterns indicative of exploitation attempts

Monitoring Recommendations

• Deploy network-level monitoring to detect anomalous traffic patterns targeting Tenda router management interfaces
• Implement logging and alerting for authentication attempts and configuration changes on affected devices
• Consider using SentinelOne Singularity to monitor network endpoints for indicators of router compromise and lateral movement

How to Mitigate CVE-2026-6632

Immediate Actions Required

• Restrict access to the Tenda F451 web management interface to trusted networks only
• Disable remote management access if not required for operations
• Implement network segmentation to isolate IoT and network infrastructure devices
• Monitor for firmware updates from Tenda that address this vulnerability

Patch Information

As of the last update on 2026-04-22, no official patch has been publicly announced by Tenda. Organizations should monitor the Tenda website for security updates and firmware releases addressing this vulnerability. The VulDB entry may also provide updated remediation information as it becomes available.

Workarounds

• Restrict web management interface access to localhost or specific trusted IP addresses using firewall rules
• Place vulnerable Tenda F451 devices behind a properly configured firewall that blocks external access to port 80/443
• Consider using a VPN for remote management access rather than exposing the web interface directly
• Implement strong authentication and change default credentials on the device

# Example: Block external access to Tenda management interface using iptables
# Run on upstream firewall or gateway device
iptables -A FORWARD -d <TENDA_IP> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <TENDA_IP> -p tcp --dport 443 -j DROP
# Allow management only from trusted admin network
iptables -I FORWARD -s <ADMIN_NETWORK>/24 -d <TENDA_IP> -p tcp --dport 80 -j ACCEPT