ICS Advisory (ICSA-16-348-05D)

Siemens S7-300/400 PLC Vulnerabilities (Update D)

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This updated advisory is a follow-up to the updated advisory titled ICSA-16-348-05C Siemens S7-300/400 PLC Vulnerabilities that was published November 28, 2017, on the NCCIC/ICS-CERT web site.

Zhu WenZhe from Beijing Acorn Network Technology has identified password leak and denial-of-service (DoS) vulnerabilities in Siemens’ S7-300 and S7-400 programmable logic controllers (PLCs). Siemens has released Security Advisory SSA-731239 with advice to mitigate these vulnerabilities.

These vulnerabilities could be exploited remotely.


Siemens reports that the vulnerabilities affect the following versions of SIMATIC PLC family:

  • SIMATIC S7-300 CPU family: All versions.
  • SIMATIC S7-400 CPU family: All versions.


Successful exploitation of these vulnerabilities could lead to a denial-of-service condition or result in credential disclosure.

Impact to individual organizations depends on many factors that are unique to each organization. NCCIC recommends that organizations evaluate the impact of these vulnerabilities based on their operational environment, architecture, and product implementation.


Siemens is a multinational company headquartered in Munich, Germany.

The affected products, SIMATIC S7-300 and S7-400 PLC family, have been designed for process control in industrial environments. According to Siemens, SIMATIC S7-300 and S7-400 PLCs are deployed across several sectors including Chemical, Energy, Food and Agriculture, and Water and Wastewater Systems. Siemens estimates that these products are used worldwide.




An attacker with network access to Port 102/TCP (ISO-TSAP) or via Profibus could obtain credentials from the PLC if Protection-level 2 is configured on the affected devices. This vulnerability affects all listed affected products.

CVE-2016-9159b has been assigned to this vulnerability. A CVSS v3 base score of 7.5 has been calculated with a CVSS vector string of: (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).c


Specially crafted packets sent to Port 80/TCP could cause the affected devices to go into defect mode. A cold restart is required to recover the system. This vulnerability affects all SIMATIC S7-300 PN CPUs, and all SIMATIC S7-400 PN V6 and V7 CPUs.

CVE-2016-9158e has been assigned to this vulnerability. A CVSS v3 base score of 7.5 has been calculated with a CVSS vector string of: (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).f



These vulnerabilities could be exploited remotely.


No known public exploits specifically target these vulnerabilities.


An attacker with a low skill would be able to exploit these vulnerabilities.


--------- Begin Update D Part 1 of 1 --------

Siemens provides the following firmware versions to resolve CVE-2016-9158:

  • SIMATIC S7-300 CPU family: Update to V3.X.14:


  • SIMATIC S7-400 PN V6: Update to V6.0.6:


  • SIMATIC S7-400 V7 CPU family: Update to V7.0.2:


  • SIMATIC S7-410 V8 CPU family: Update to V8.2:


 --------- End Update D Part 1 of 1 ----------

Siemens recommends activating Field Interface Security in PCS 7 V9.0, and using a CP 443-1 Advanced to communicate with ES/OS in order to mitigate CVE-2016-9159.

Siemens also recommends the following mitigations:

  • Deactivate the web server.
  • Apply Protection-level 3 read/write protection.
  • Apply cell protection concept.
  • Apply defense-in-depth strategies.
  • Use VPN for protecting network communication between cells.

Siemens strongly recommends users protect network access with appropriate mechanisms (e.g., firewalls, segmentation, VPN). Siemens also advises that users configure the operational environment according to Siemens’ Operational Guidelines for Industrial Security:


For more information on this vulnerability and more detailed mitigation instructions, please see Siemens Security Advisory SSA-731239 at the following location:


NCCIC recommends 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.

NCCIC reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures.

NCCIC 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 NCCIC 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 NCCIC for tracking and correlation against other incidents.

  • a. CWE- 326: Inadequate Encryption Strength, https://cwe.mitre.org/data/definitions/326.html, web site last accessed December 13, 2016.
  • b. NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-9159, 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, http://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N, web site last accessed December 13, 2016.
  • d. CWE-693: Protection Mechanism Failure, https://cwe.mitre.org/data/definitions/693.html, web site last accessed December 13, 2016.
  • e. NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-9158, NIST uses this advisory to create the CVE web site report. This web site will be active sometime after publication of this advisory.
  • f. CVSS Calculator, https://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H, web site last accessed December 13, 2016.

Contact Information

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

Email: CISAservicedesk@cisa.dhs.gov
Toll Free: 1-888-282-0870

For industrial control systems cybersecurity information:  https://www.us-cert.gov/ics 
or incident reporting:  https://www.us-cert.gov/report

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