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             AUSCERT External Security Bulletin Redistribution

           Moxa UC 7408-LX-Plus Firmware Overwrite Vulnerability
                                1 June 2016


        AusCERT Security Bulletin Summary

Product:           Moxa UC 7408-LX-Plus
Publisher:         ICS-CERT
Operating System:  Network Appliance
Impact/Access:     Overwrite Arbitrary Files -- Existing Account
Resolution:        Mitigation
CVE Names:         CVE-2016-4500  

Original Bulletin: 

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Advisory (ICSA-16-152-01)

Moxa UC 7408-LX-Plus Firmware Overwrite Vulnerability

Original release date: May 31, 2016

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NCCIC/ICS-CERT has received information from a third party that identified a 
firmware overwrite vulnerability in Moxas UC 7408-LX-Plus device. Moxa has 
produced instructions to reduce exposure to this vulnerability. The Moxa UC 
7408-LX-Plus device has been discontinued.

This vulnerability could be exploited remotely.


The following Moxa UC-7408 versions are affected:

    UC-7408 LX-Plus all versions.


A firmware overwrite has been used that is neither recoverable in the field or
by the manufacturer, necessitating the replacement of the device.

Impact to individual organizations depends on many factors that are unique to
each organization. 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, UC-7408-LX-Plus, is an embedded computer. According to 
Moxa, these computers are deployed across several sectors, including Chemical,
Commercial Facilities, Critical Manufacturing, Emergency Services, Energy, 
Food and Agriculture, Government Facilities, Water and Wastewater Systems, and
others. Moxa estimates that this product is used globally but concentrated in
the US, Europe, Chile, Argentina, Peru, Columbia, and Taiwan, with 50 to 60 
percent of all sales in the US.




The firmware overwrite is neither recoverable in the field or by the 
manufacturer, necessitating the replacement of the device.

CVE-2016-4500 [b] has been assigned to this vulnerability. A CVSS v3 base score 
of 5.8 has been assigned; the CVSS vector string is 
(AV:N/AC:H/PR:H/UI:N/S:C/C:N/I:N/A:H). [c]



This vulnerability could be exploited remotely.


No known public exploits specifically target this vulnerability.


Crafting a working exploit for this vulnerability would be difficult. Root 
level access is necessary for this exploit. This decreases the likelihood of a
successful exploit.


Moxa recommends the following suggestions to reduce the risk of unauthorized 
access to UC 7408-LX-Plus:

Strengthen authentication requirements:

- - Change passwords for administrative users periodically.

- - Use the stronger password. Ex: mixed with upper and lower case character and 

- - Disable or delete unused profiles from system.

- - Provide login authentication at all access portals before accessing this 
device ex: console, ssh, web.

- - Disable unnecessary services.

- - Enable system log for monitoring.

- - Log unsuccessful login attempts.

- - Auto log out from ssh or telnet console after a period of inactivity.

Increase access control:

- - Restrict mobile code download and execution.

- - Limit the number of concurrent sessions. Ex: SSH is limited to 5.

- - Log the access control information with timestamps for audit purpose.

Enhance data integrity:

- - Use secure transmission protocol, SSH, VPN, HTTPS, etc., to protect 
integrity of information.

Enhance data confidentiality:

- - Remove the shared data if the shared resource is not used.

Restrict data flow:

- - Enable firewall function for deny all accept exception rule.

ICS-CERT recommends that users take defensive measures to minimize the risk of
exploitation of these vulnerabilities. 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 ICSCERT 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 

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.

a. CWE-306: Missing Authentication for Critical Function, 
http://cwe.mitre.org/data/definitions/306.html, web site last accessed May 31,

b. NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-4500, NIST 
uses this advisory to create the CVE web site report. This web site will be 
active sometime after publication of this advisory.

c. CVSS Calculator, 
web site last accessed May 31, 2016.

Contact Information

For any questions related to this report, please contact ICS-CERT at:

Email: ics-cert@hq.dhs.gov (link sends e-mail)

Toll Free: 1-877-776-7585

International Callers: (208) 526-0900

For industrial control systems security information and incident reporting: 

ICS-CERT continuously strives to improve its products and services. You can 
help by choosing one of the links below to provide feedback about this 

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