Routers are among the most critical devices in modern networking, serving as gateways between private systems and the wider internet. They manage vast amounts of sensitive data, control network traffic, and ensure secure communication for both personal and business environments. Because of their importance, routers are a frequent target for attackers who aim to exploit weaknesses and gain unauthorized control.

Unfortunately, not all vulnerabilities are purely remote. Some exist at the hardware or interface level, providing hidden entry points that attackers with physical access can abuse. These often-overlooked flaws can lead to full system compromise and put confidential data at risk.

In this blog, we will explore CVE-2024–4231, a recently documented vulnerability in the Digisol DG-GR1321 router that stems from improper access control on its UART/Serial interface. We'll break down how the flaw works, its potential impact, and steps you can take to mitigate the risks.

Vulnerability Overview

The vulnerability affects the Digisol DG-GR1321 router (Hardware version 3.7L; Firmware version v3.2.02). The issue lies in the router's UART/Serial interface, which provides system logs during boot and direct access to the root shell. Unfortunately, this interface lacks proper authentication, enabling attackers to connect and issue commands with full privileges.

  • Affected Device: Digisol DG-GR1321
  • Hardware Version: 3.7L
  • Firmware Version: v3.2.02
  • CVE Identifier: CVE-2024–4231
  • Type of Vulnerability: Improper Access Control

Technical Details

The UART/Serial interface is exposed on the router's PCB and is composed of four pins: Rx, Tx, Vcc, and Gnd.

Key specifications:

  • Signal Type: TTL level
  • Baud Rate: 115200
  • Functions:
  • Outputs logs during device boot
  • Provides access to the root shell

Critical weakness:

  • No authentication required for root shell access
  • Allows attackers to execute commands with unrestricted privileges

Proof of Concept (PoC)

The exploitation process for CVE-2024–4231 involves straightforward hardware interaction:

  1. Identify UART Pins — Locate the Rx, Tx, Vcc, and Gnd pins on the PCB.
  2. Establish a Connection — Use a UART-to-USB adapter with terminal emulator software.
  3. View Boot Logs — Monitor system log messages during startup.
  4. Gain Root Access — The terminal grants a root shell prompt without requiring credentials.

This confirms that an attacker can gain full control over the device.

Impact of the Vulnerability

Successful exploitation of this vulnerability allows attackers to:

  • Access Root Privileges: Gain complete administrative control of the router.
  • Extract Data: Steal sensitive configuration details and stored information.
  • Manipulate Traffic: Monitor or alter network traffic passing through the device.
  • Compromise Network Security: Undermine confidentiality, integrity, and availability of connected systems.

While the attack requires physical access, the implications are serious in shared or enterprise environments where routers are not always physically secured.

Mitigation

The most effective way to mitigate this vulnerability is to upgrade the firmware to the latest version provided by Digisol. Updated firmware packages address security flaws and may patch this specific issue.

Recommendation: Always keep network hardware updated with the latest firmware releases and disable unnecessary debug interfaces where possible.

TL;DR

  • Vulnerability: Improper Access Control (CVE-2024–4231)
  • Device: Digisol DG-GR1321 (HW v3.7L; FW v3.2.02)
  • Issue: Unauthenticated root shell access through UART interface
  • Impact: Full device compromise, sensitive data exposure, traffic manipulation
  • Fix: Upgrade to the latest firmware version

Final Thoughts

CVE-2024–4231 is a strong reminder that hardware-level vulnerabilities can be just as dangerous as remote exploits. Debugging interfaces like UART are often overlooked but can provide attackers with powerful entry points when left unsecured.

At Redfox Security, we work with organizations to uncover these hidden risks and strengthen defenses across both hardware and software layers. From penetration testing and vulnerability assessments to security training and consulting, our experts ensure that your systems are better protected against emerging threats.

If you want to assess your organization's exposure to vulnerabilities like CVE-2024–4231, get in touch with us today. We also offer training programs designed to equip professionals with the skills needed to detect, exploit, and mitigate such flaws before attackers can.