CVE-2026-6630: Tenda F451 Buffer Overflow Vulnerability

CVE-2026-6630 Overview

CVE-2026-6630 is a buffer overflow vulnerability in the Tenda F451 router running firmware version 1.0.0.7_cn_svn7958. The flaw resides in the fromGstDhcpSetSer function within the /goform/GstDhcpSetSer endpoint of the device's httpd web service. Attackers can manipulate the dips argument to trigger memory corruption [CWE-119]. The issue is remotely exploitable across the network, and a public exploit has been disclosed, increasing the likelihood of opportunistic abuse against exposed devices.

Critical Impact
Remote attackers with low privileges can corrupt memory through the dips parameter, potentially leading to denial of service or arbitrary code execution on the router.

Affected Products

Tenda F451 router
Firmware version 1.0.0.7_cn_svn7958
httpd component handling /goform/GstDhcpSetSer

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

The vulnerability affects the embedded web server (httpd) running on the Tenda F451 router. The fromGstDhcpSetSer handler processes DHCP server configuration requests sent to /goform/GstDhcpSetSer. The function copies the user-supplied dips argument into a fixed-size buffer without proper bounds checking, causing a classic buffer overflow [CWE-119].

Because the vulnerable endpoint is reachable over the network, attackers can send a crafted HTTP request to overwrite adjacent memory. Successful exploitation can disrupt router operation or allow execution of attacker-controlled instructions, depending on memory layout and protections compiled into the firmware.

Root Cause

The root cause is improper restriction of operations within the bounds of a memory buffer. The dips parameter handler in fromGstDhcpSetSer lacks input length validation before copying data into a stack-based buffer, allowing oversized input to overwrite control flow data.

Attack Vector

An authenticated user on the network can issue a crafted HTTP POST request to /goform/GstDhcpSetSer with an oversized dips value. The vulnerability requires low privileges and no user interaction. Public proof-of-concept material referenced in the GitHub Issue Discussion and VulDB Vulnerability Details describes the parameter manipulation pattern.

The vulnerability is described in prose only — no verified exploit code is reproduced here. Consult the referenced advisories for technical specifics.

Detection Methods for CVE-2026-6630

Indicators of Compromise

HTTP POST requests to /goform/GstDhcpSetSer containing abnormally long dips parameter values.
Unexpected httpd process crashes or restarts on Tenda F451 devices.
Configuration changes to DHCP server settings that were not initiated by an administrator.

Detection Strategies

Inspect HTTP traffic destined for the router management interface and flag requests where the dips field exceeds expected length thresholds.
Monitor router system logs for httpd segmentation faults or watchdog-triggered reboots.
Correlate authentication events with subsequent administrative endpoint access to detect low-privileged accounts probing goform handlers.

Monitoring Recommendations

Capture and retain web management traffic to Tenda F451 devices for retrospective analysis.
Alert on outbound connections initiated by the router that deviate from baseline behavior, which may indicate post-exploitation activity.
Track firmware integrity and configuration drift across the device fleet.

How to Mitigate CVE-2026-6630

Immediate Actions Required

Restrict access to the router's web management interface so it is reachable only from trusted management networks.
Disable remote (WAN-side) administration on all Tenda F451 devices.
Rotate administrative credentials and enforce strong, unique passwords to reduce the value of stolen low-privilege accounts.
Audit DHCP server configurations on affected devices for unauthorized modifications.

Patch Information

At the time of publication, no vendor patch has been referenced in the NVD entry. Review the Tenda Website Security portal and the VulDB CTI Information page for updates. Apply firmware updates as soon as the vendor releases a fixed version.

Workarounds

Place affected routers behind a perimeter firewall and block external access to TCP ports used by the management interface.
Segment the management network from user and guest networks to limit lateral exposure.
Replace end-of-life or unsupported Tenda F451 hardware with currently maintained devices where feasible.

bash

# Example: block external access to the router management port using iptables on an upstream gateway
iptables -A FORWARD -p tcp --dport 80 -d <router_ip> -j DROP
iptables -A FORWARD -p tcp --dport 443 -d <router_ip> -j DROP