ICS Advisory

Sixnet BT Series Hard-coded Credentials Vulnerability

Last Revised
Alert Code


Independent researcher Neil Smith has identified a hard-coded credential vulnerability in Sixnet’s BT series routers. Sixnet has produced patches and new firmware to mitigate this vulnerability.

This vulnerability could be exploited remotely. Exploits that target this vulnerability are known to be publicly available.


Sixnet reports that the vulnerability affects the following products:

  • Sixnet BT-5xxx and BT-6xxx series M2M cellular routers versions prior to 3.8.21.


An attacker could exploit the hard-coded factory password to gain full access to the affected device.

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.


Sixnet is a US-based company owned by Red Lion Controls.

The affected products, Sixnet BT series routers, are used for providing high-speed, secure wireless connectivity to critical assets and devices at remote sites. According to Sixnet, the BT series routers are deployed across several sectors including Commercial Facilities, Energy, Financial Services, and Transportation Systems. Sixnet estimates that these products are used primarily in North America, Europe, and Asia.



USE OF HARD-CODED CREDENTIALSCWE-798: Use of Hard-coded Credentials, http://cwe.mitre.org/data/definitions/798.html, web site last accessed May 26, 2016.

There are hard-coded factory accounts on these devices.

CVE-2016-4521NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-4521, 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 9.8 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).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:H, web site last accessed May 26, 2016.



This vulnerability could be exploited remotely.


Exploits that target this vulnerability are publicly available.


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


Sixnet has produced patches and new firmware (versions 3.8.21 or 3.9.8) to address this issue. Users are recommended to install the latest version. Firmware and release notes can be found on Sixnet’s software and firmware page at the following location:


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.