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Advisory (ICSA-17-192-01)

Siemens SIMATIC Logon

Original release date: July 11, 2017

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CVSS v3 5.3

ATTENTION: Remotely exploitable/low skill level to exploit.

Vendor: Siemens

Equipment: SIMATIC Logon

Vulnerability: Out-of-Bounds Write


Siemens reports that the vulnerability affects the following SIMATIC Logon products:

  • SIMATIC Logon: All versions prior to V1.6


Successful exploitation of this vulnerability could allow attackers to cause a denial of service of the SIMATIC Logon Remote Access service under certain conditions.


Siemens created a software upgrade V1.6 for SIMATIC Logon which fixes the vulnerability, and they recommend users upgrade to the newest version. Please contact the local Siemens representative or customer support at the following location:


Siemens strongly recommends users protect network access to the Port 16389/TCP of the SIMATIC Logon Remote Access service with appropriate mechanisms. Siemens also advises that users configure the operational environment according to Siemens’ Operational Guidelines for Industrial Security:


For a more specific list of affected products and more detailed mitigation instructions, please see Siemens Security Advisory SSA-804859 at the following location:


NCCIC/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. 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 this vulnerability.


Specially crafted packets sent to the SIMATIC Logon Remote Access service on Port 16389/TCP could cause a denial-of-service condition. The service restarts automatically.

CVE-2017-9938 has been assigned to this vulnerability. A CVSS v3 base score of 5.3 has been assigned; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L).


Tenable Network Security reported this vulnerability to Siemens.


Critical Infrastructure Sectors: Chemical, Energy, Food and Agriculture, Water and Wastewater Systems

Countries/Areas Deployed: Worldwide

Company Headquarters Location: Germany

Contact Information

For any questions related to this report, please contact the NCCIC at:

Toll Free: 1-888-282-0870

For industrial control systems cybersecurity information:  http://ics-cert.us-cert.gov 
or incident reporting:  https://ics-cert.us-cert.gov/Report-Incident?

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