CVE-2026-3399:

Overview

A high-severity security vulnerability has been identified in the Tenda F453 router, firmware version 1.0.0.3. This flaw is a buffer overflow in the device’s web management interface, which can be exploited by a remote attacker without requiring authentication. The vulnerability is in a specific function that handles DHCP server settings.

Vulnerability Explained

In simple terms, the router’s web configuration software (httpd) contains a programming error. The function that processes DHCP server data does not properly check the size of the input it receives. By sending an overly long, specially crafted string to a specific web endpoint (/goform/GstDhcpSetSer), an attacker can overflow a memory buffer. This can corrupt the router’s normal operation and allow the attacker to run their own malicious code on the device.

Potential Impact

The primary risk is that an attacker could gain full control of the affected router. This could lead to several serious consequences:

• Network Compromise: The attacker could intercept, redirect, or inspect all internet traffic passing through the router.
• Malware Deployment: The router could be used to launch further attacks against devices on the local network.
• Denial of Service: The router could be crashed, causing a complete loss of internet connectivity for all connected users.
• Persistence: Attackers could install backdoors, making the compromise difficult to remove without a full reset.

The severity is increased because the exploit is publicly available, lowering the barrier for attackers to use it.

Remediation and Mitigation

Immediate Action Required: Due to the public exploit and high severity, affected users should act promptly.

1. Check Firmware Version: Confirm your Tenda F453 is running the vulnerable firmware version 1.0.0.3. This is typically found in the router’s web admin panel.
2. Apply Vendor Updates: Immediately check the official Tenda website for a firmware update that addresses CVE-2026-3399. If an update is available, install it without delay. This is the only complete solution.
3. If No Update is Available: If the vendor has not released a patch, consider the following risk-mitigation steps:
   • Disable Remote Administration: Ensure the router’s web management interface is not accessible from the internet (WAN). It should only be accessible from your local network (LAN).
   • Network Segmentation: Place sensitive devices on a separate network segment if possible.
   • Consider Replacement: For critical deployments, replacing the router with a model from a vendor that provides active security updates may be necessary.
4. Monitor Vendor Communications: Regularly check Tenda’s security advisories for patch information and further guidance.