ICS Advisory

Moxa MGate Authentication Bypass Vulnerability

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Alert Code


Independent researcher Maxim Rupp has identified an authentication bypass vulnerability in Moxa’s MGate products. Moxa has produced new firmware versions to mitigate this vulnerability.

This vulnerability could be exploited remotely.


Moxa reports that the vulnerability affects the following products:

  • MGate MB3180, versions prior to v1.8,
  • MGate MB3280, versions prior to v2.7,
  • MGate MB3480, versions prior to v2.6,
  • MGate MB3170, versions prior to v2.5, and
  • MGate MB3270, versions prior to v2.7


A successful exploit of this vulnerability may allow an attacker to log in as a valid user.

Impact to individual organizations depends on many factors that are unique to each organization. NCCIC/ICS-CERT recommends that organizations evaluate the impact of this vulnerability based on their operational environment, architecture, and product implementation.


Moxa is a Taiwan-based company that maintains offices in several countries around the world, including the US, UK, India, Germany, France, China, Russia, and Brazil.

The affected product, MGate, is a serial to Ethernet modbus gateway. According to Moxa, MGate is deployed across several sectors, including Chemical, Commercial Facilities, Critical Manufacturing, Emergency Services, Energy, Food and Agriculture, Government Facilities, and Water and Wastewater Systems. Moxa estimates that this product is used globally but concentrated in the US, Europe, South America, and Taiwan.



INADEQUATE ENCRYPTION STRENGTHCWE-326: Inadequate Encryption Strength, http://cwe.mitre.org/data/definitions/326.html, web site last accessed July 14, 2016.

An attacker can use accessible information to brute force a parameter that will allow a bypass of authentication mechanisms.

CVE-2016-5804NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-5804, NIST uses this advisory to create the CVE web site report. This web site will be active sometime after publication of this advisory. has been assigned to this vulnerability. A CVSS v3 base score of 9.1 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N).CVSS Calculator, https://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N, web site last accessed July 14, 2016.



This vulnerability could be exploited remotely.


No known public exploits specifically target this vulnerability.


An attacker with a low skill would be able to exploit this vulnerability.


Moxa has released new versions of firmware, which has enhanced the security of the MB3x70 and MB3x80 families. This new firmware can be located on its web site at the following locations:

  • MB3180, v1.8, MB3280, v2.7, and MB3480, v2.6


  • MB3170, v2.5 and MB3270, v2.7


ICS-CERT recommends that users take defensive measures to minimize the risk of exploitation of this vulnerability. Specifically, users should:

  • Minimize network exposure for all control system devices and/or systems, and ensure that they are not accessible from the Internet.
  • Locate control system networks and remote devices behind firewalls, and isolate them from the business network.
  • When remote access is required, use secure methods, such as Virtual Private Networks (VPNs), recognizing that VPNs may have vulnerabilities and should be updated to the most current version available. Also recognize that VPN is only as secure as the connected devices.

ICS-CERT reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures.

ICS-CERT also provides a section for control systems security recommended practices on the ICS-CERT web page at: http://ics-cert.us-cert.gov/content/recommended-practices. Several recommended practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies.

Additional mitigation guidance and recommended practices are publicly available in the ICS‑CERT Technical Information Paper, ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation Strategies, that is available for download from the ICS-CERT web site (http://ics-cert.us-cert.gov/).

Organizations observing any suspected malicious activity should follow their established internal procedures and report their findings to ICS-CERT for tracking and correlation against other incidents.

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