CVE-2026-0715

Executive Summary

CVE-2026-0715 describes a physical access vulnerability in Moxa Arm-based industrial computers running Moxa Industrial Linux Secure. The device uses a device-unique bootloader password that is provided on the device itself. An attacker with physical access can use this password to access the bootloader menu via a serial interface. While the bootloader enforces digital signature verification and only permits flashing of Moxa-signed images, an attacker could cause a temporary denial-of-service condition by reflashing a valid image. Remote exploitation is not possible, and full system takeover or privilege escalation is not achievable.

Key Risk: Physical access to the device allows an attacker to enter the bootloader menu, potentially causing a denial-of-service by reflashing a valid signed image. The impact is limited to temporary disruption.

Affected Ecosystem: Moxa Industrial Linux Secure on Arm-based industrial computers.

Supply Chain & Package Security: This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a hardware/firmware-level issue specific to Moxa industrial devices.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (NVD assigned, but based on description, a physical attack vector with limited impact)
• Attack Vector (AV): Physical (AV:P) – Requires physical access to the device.
• Attack Complexity (AC): Low (AC:L) – The bootloader password is provided on the device.
• Privileges Required (PR): None (PR:N) – No authentication needed beyond physical access.
• User Interaction (UI): None (UI:N) – No user interaction required.
• Scope (S): Unchanged (S:U) – The vulnerability does not cross a trust boundary.
• Confidentiality (C): None (C:N) – No data exposure.
• Integrity (I): None (I:N) – Cannot install malicious firmware.
• Availability (A): Low (A:L) – Potential temporary denial-of-service by reflashing a valid image.

Threat Level: Low. The attack requires physical access and does not allow full compromise. The primary risk is a temporary denial-of-service.

Deep Dive & Mechanics

The vulnerability stems from the device-unique bootloader password being physically accessible on the device. This password is intended for legitimate maintenance but can be used by an attacker with physical access to enter the bootloader menu via a serial interface.

Technical Details:

• The bootloader menu is accessible via a serial console.
• The password is device-unique but printed or stored on the device itself.
• Once in the bootloader menu, the attacker can reflash a valid Moxa-signed image.
• The bootloader enforces digital signature verification, preventing installation of unsigned or malicious firmware.
• The attacker cannot execute arbitrary code or gain elevated privileges.

Attack Flow:

1. Attacker gains physical access to the Moxa device.
2. Attacker connects to the device via a serial interface (e.g., UART).
3. Attacker reads the bootloader password from the device label or documentation.
4. Attacker enters the bootloader menu using the password.
5. Attacker reflashes a valid Moxa-signed image, causing a temporary denial-of-service (device reboot or reconfiguration).

Root Cause: The bootloader password is physically exposed on the device, allowing unauthorized access to the bootloader menu.

Vulnerable vs. Patched Code

No code snippets are available for this vulnerability. The issue is not a software code flaw but a design weakness in how the bootloader password is managed. A patch would likely involve:

• Removing the physical exposure of the bootloader password.
• Requiring additional authentication (e.g., a user-set password) for bootloader access.
• Implementing rate-limiting or lockout mechanisms for bootloader access attempts.

Exploitation & Lab Setup

Red Team

Prerequisites:

• Physical access to a Moxa Arm-based industrial computer running Moxa Industrial Linux Secure.
• Serial console cable (e.g., USB-to-UART adapter).
• Terminal emulator (e.g., PuTTY, screen, minicom).

Exploitation Steps:

1. Connect the serial console cable to the device's UART port.
2. Open a terminal emulator with the correct baud rate (typically 115200).
3. Power on or reset the device.
4. Interrupt the boot process (e.g., press a key like Enter or Space) to enter the bootloader menu.
5. When prompted for the password, enter the device-unique password found on the device label.
6. Once in the bootloader menu, select the option to flash a new image.
7. Provide a valid Moxa-signed firmware image (e.g., from Moxa's official site).
8. Confirm the flash operation, causing the device to reboot with the reflashed image.

Note: This does not allow installation of malicious firmware. The impact is limited to a temporary denial-of-service.

Blue Team

Detection:

• Monitor for physical access attempts to devices (e.g., security cameras, door logs).
• Check serial console logs for unauthorized bootloader menu access.
• Use tamper-evident seals on device chassis to detect physical intrusion.

Prevention:

• Store devices in physically secure locations (e.g., locked cabinets, server rooms).
• Disable serial console access if not needed.
• Implement a custom bootloader password that is not physically exposed.
• Use hardware security modules (HSMs) to protect bootloader credentials.

Response:

• If unauthorized bootloader access is detected, isolate the device and reflash with a known-good firmware.
• Review physical security logs to identify the attacker.
• Rotate any credentials that may have been exposed.

Indicators of Compromise (IOCs)

• Physical Access: Unauthorized physical presence near Moxa devices.
• Serial Console Activity: Unexpected serial console connections to the device.
• Bootloader Menu Access: Logs showing bootloader menu entry with the device-unique password.
• Firmware Reflash Events: Unexpected firmware reflash operations.
• Device Reboots: Unexplained device reboots or reconfigurations.

Detection Engineering

YARA Rule

rule Moxa_Bootloader_Password_Exposure {
    meta:
        description = "Detects references to Moxa bootloader password exposure"
        author = "Valters IT"
        date = "2026-02-18"
        reference = "CVE-2026-0715"
    strings:
        $s1 = "bootloader password" nocase
        $s2 = "Moxa Industrial Linux" nocase
        $s3 = "serial interface" nocase
    condition:
        all of ($s1, $s2, $s3)
}

Sigma Rule

title: Moxa Bootloader Password Exposure
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects attempts to access Moxa bootloader menu via serial interface
author: Valters IT
date: 2026-02-18
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-0715
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        CommandLine|contains:
            - "bootloader"
            - "serial"
            - "Moxa"
    condition: selection
falsepositives:
    - Legitimate maintenance activities
level: low

Suricata Rule

alert tcp any any -> any any (msg:"Moxa Bootloader Password Exposure Attempt"; flow:to_server; content:"bootloader"; nocase; content:"password"; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Physical Security: Ensure Moxa devices are in physically secure locations (locked cabinets, restricted access).
2. Disable Serial Console: If not required for maintenance, disable the serial console interface.
3. Change Bootloader Password: If possible, change the bootloader password to a custom, non-exposed value.
4. Monitor Physical Access: Implement surveillance and access logs for device locations.

Long-Term Fix:

• Moxa should release a firmware update that removes the physical exposure of the bootloader password or implements additional authentication (e.g., multi-factor).
• Consider using hardware security modules (HSMs) to store bootloader credentials securely.

Workarounds:

• Use tamper-evident seals to detect physical intrusion.
• Implement network-based monitoring for unexpected device behavior (e.g., reboots, firmware changes).

Valters IT
DevSecOps & Cyber Threat Intelligence Expert