CVE-2026-6631: Tenda F451 Buffer Overflow Vulnerability

CVE-2026-6631 Overview

A buffer overflow vulnerability has been identified in Tenda F451 router firmware version 1.0.0.7_cn_svn7958. The vulnerability affects the fromwebExcptypemanFilter function within the /goform/webExcptypemanFilter endpoint of the httpd web service component. By manipulating the page argument, an attacker can trigger a buffer overflow condition that may lead to memory corruption and potential remote code execution.

Critical Impact

This network-accessible buffer overflow vulnerability in Tenda F451 routers can be exploited remotely with low authentication requirements, potentially allowing attackers to compromise affected devices and gain unauthorized control over network infrastructure.

Affected Products

• Tenda F451 Firmware Version 1.0.0.7_cn_svn7958
• Tenda F451 httpd web service component
• /goform/webExcptypemanFilter endpoint

Discovery Timeline

• April 20, 2026 - CVE-2026-6631 published to NVD
• April 22, 2026 - Last updated in NVD database

Technical Details for CVE-2026-6631

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), which represents a fundamental memory safety issue in the affected firmware. The vulnerable function fromwebExcptypemanFilter fails to properly validate the length of user-supplied input through the page parameter before copying it into a fixed-size memory buffer.

When processing HTTP requests to the /goform/webExcptypemanFilter endpoint, the httpd service does not enforce adequate boundary checks on incoming data. This allows an attacker to supply an oversized value that exceeds the allocated buffer space, overwriting adjacent memory regions including potentially critical control structures such as return addresses or function pointers.

The exploit has been publicly disclosed, increasing the urgency for organizations to address this vulnerability on any affected Tenda F451 devices in their networks.

Root Cause

The root cause stems from inadequate input validation within the fromwebExcptypemanFilter function. The code fails to verify that the length of the page argument does not exceed the size of the destination buffer before performing memory copy operations. This classic buffer overflow pattern is common in embedded device firmware where memory-safe programming practices may not be consistently applied.

Attack Vector

The attack is network-accessible and requires low-privilege authentication to exploit. An attacker can craft malicious HTTP requests targeting the /goform/webExcptypemanFilter endpoint with an oversized page parameter value. When the httpd service processes this request, the buffer overflow occurs, potentially allowing the attacker to:

1. Corrupt adjacent memory structures
2. Overwrite return addresses on the stack
3. Redirect program execution to attacker-controlled code
4. Achieve remote code execution on the affected router

The vulnerability is particularly concerning as routers often occupy privileged network positions, making compromise of these devices valuable for lateral movement or establishing persistent network access.

Detection Methods for CVE-2026-6631

Indicators of Compromise

• Unusual HTTP POST requests to /goform/webExcptypemanFilter with abnormally large page parameter values
• Unexpected router reboots or service crashes in the httpd component
• Anomalous outbound network connections originating from the router
• Suspicious modifications to router configuration or firmware

Detection Strategies

• Monitor web server logs for malformed or oversized requests to /goform/webExcptypemanFilter
• Deploy network intrusion detection rules to identify buffer overflow attack patterns targeting Tenda devices
• Implement traffic analysis to detect unusual request patterns to the affected endpoint
• Configure alerts for httpd service crashes or unexpected restarts on Tenda F451 routers

Monitoring Recommendations

• Enable comprehensive logging on network perimeter devices monitoring traffic to Tenda routers
• Implement behavioral analysis to detect post-exploitation activities from compromised router IP addresses
• Establish baseline network behavior for router management interfaces to identify anomalous access patterns
• Review authentication logs for unauthorized access attempts to router administration interfaces

How to Mitigate CVE-2026-6631

Immediate Actions Required

• Restrict network access to the router's web administration interface to trusted management networks only
• Implement firewall rules to block external access to the /goform/webExcptypemanFilter endpoint
• Consider disabling the web-based administration interface if not required for operations
• Monitor for any vendor firmware updates from Tenda addressing this vulnerability

Patch Information

At the time of publication, no official patch information is available from Tenda. Organizations should monitor the Tenda Official Website for firmware updates addressing this vulnerability. Additional technical details are available through the VulDB Vulnerability Report and the GitHub Issue Tracker Entry.

Workarounds

• Isolate affected Tenda F451 routers on a separate network segment with restricted access
• Implement network-level access controls to limit which IP addresses can reach the router's management interface
• Use a Web Application Firewall (WAF) to filter oversized parameter values in requests to the affected endpoint
• Consider replacing vulnerable devices with alternative hardware if patches are not forthcoming from the vendor