CVE-2026-6632: Tenda F451 Buffer Overflow Vulnerability

CVE-2026-6632 Overview

CVE-2026-6632 is a buffer overflow vulnerability in the Tenda F451 router running firmware version 1.0.0.7_cn_svn7958. The flaw resides in the fromSafeClientFilter function within /goform/SafeClientFilter, part of the router's httpd web management component. Attackers manipulate the menufacturer and Go parameters to overflow a fixed-size buffer. The vulnerability is exploitable remotely over the network and a public exploit is referenced in third-party vulnerability databases. The weakness is classified under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer).

Critical Impact

Remote attackers with low-privilege access can corrupt memory in the router's HTTP daemon, enabling denial of service or arbitrary code execution on the embedded device.

Affected Products

• Tenda F451 router
• Firmware version 1.0.0.7_cn_svn7958
• httpd web management component handling /goform/SafeClientFilter

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

The vulnerability lives inside the fromSafeClientFilter handler exposed by the router's httpd binary at the /goform/SafeClientFilter endpoint. This handler processes client filtering rules submitted from the device's web administration interface. The handler reads attacker-controlled values for the menufacturer and Go HTTP parameters and copies them into stack or heap buffers without verifying the input length.

Because the affected device is an embedded Linux router using a non-hardened HTTP daemon, oversized parameter values overwrite adjacent memory. Successful exploitation can corrupt return addresses, function pointers, or heap metadata in the httpd process. The CWE classification of [CWE-119] confirms the issue is a memory boundary violation rather than a logic flaw.

Root Cause

The root cause is the absence of bounds checking before string operations copy menufacturer and Go parameter values into fixed-size buffers. Embedded router firmware frequently uses unsafe routines such as strcpy or sprintf to populate request-handling structures. With no length validation in fromSafeClientFilter, an attacker controls how many bytes land in memory.

Attack Vector

The attack vector is the network-facing web management interface. An authenticated attacker, or any user who can reach the management UI from a reachable network segment, sends a crafted POST request to /goform/SafeClientFilter. The request supplies oversized menufacturer and Go values designed to trigger the overflow. The CVSS 4.0 vector indicates low privileges are required and no user interaction is needed, leaving the router exposed wherever the management interface is reachable.

No verified proof-of-concept code is reproduced here. Refer to the GitHub Issue Discussion and VulDB Vulnerability Details for technical specifics.

Detection Methods for CVE-2026-6632

Indicators of Compromise

• HTTP POST requests to /goform/SafeClientFilter containing unusually long menufacturer or Go parameter values.
• Unexpected restarts or crash logs from the httpd process on Tenda F451 devices.
• Outbound connections from the router to unknown hosts following management-interface traffic.

Detection Strategies

• Inspect web server and proxy logs for POST bodies to /goform/SafeClientFilter exceeding expected parameter lengths.
• Deploy network IDS signatures that flag oversized form fields submitted to Tenda router management endpoints.
• Correlate router crash events with preceding HTTP traffic to identify exploitation attempts.

Monitoring Recommendations

• Restrict and monitor administrative access to router management interfaces from internal networks only.
• Capture and review syslog output from Tenda F451 devices for httpd segmentation faults or watchdog restarts.
• Alert on any external source attempting to reach /goform/ URIs on edge devices.

How to Mitigate CVE-2026-6632

Immediate Actions Required

• Block external access to the Tenda F451 web management interface at the perimeter firewall.
• Limit management access to a dedicated administrative VLAN with strong authentication.
• Audit all Tenda F451 devices in the environment and confirm firmware version against 1.0.0.7_cn_svn7958.

Patch Information

At the time of publication, no vendor patch is referenced in the NVD entry. Monitor the Tenda Official Website for firmware updates addressing the fromSafeClientFilter boundary issue. Track the VulDB Vulnerability Details page for status changes.

Workarounds

• Disable remote web administration on the WAN interface until a patched firmware release is available.
• Place affected devices behind a segmentation boundary that restricts who can reach /goform/SafeClientFilter.
• Replace end-of-life or unsupported Tenda F451 units with currently supported hardware where feasible.

# Example: restrict access to the router management interface using iptables on an upstream gateway
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -s <admin_subnet> -j ACCEPT
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -j DROP