ICS Advisory


Last Revised
Alert Code

CVSS v3 8.6

ATTENTION: Remotely exploitable/low skill level to exploit


Equipment: mGuard

Vulnerabilities: Resource Exhaustion, Improper Authentication


The following versions of mGuard, a network device, are affected:

  • mGuard firmware versions 8.3.0 to 8.4.2


Successful exploitation of these vulnerabilities could allow an attacker to disrupt the availability of the device and gain unauthorized access to the device.


PHOENIX CONTACT recommends that users upgrade to firmware Version 8.5.0, or higher, to mitigate the vulnerabilities.

NCCIC/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. 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.

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.

No known public exploits specifically target these vulnerabilities.


An attacker may compromise the device’s availability by performing multiple initial VPN requests.

CVE-2017-7935 has been assigned to this vulnerability. A CVSS v3 base score of 8.6 has been assigned; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H).

An attacker may be able to gain unauthorized access to the user firewall when RADIUS servers are unreachable.

CVE-2017-7937 has been assigned to this vulnerability. A CVSS v3 base score of 4.0 has been assigned; the CVSS vector string is (AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N).


PHOENIX CONTACT self-reported these vulnerabilities.


Critical Infrastructure Sector: Critical Manufacturing

Countries/Areas Deployed: Worldwide

Company Headquarters Location: Germany

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