Siemens SIMATIC S7-1200 (Update A)

1. EXECUTIVE SUMMARY

• CVSS v3 8.1
• ATTENTION: Exploitable remotely
• Vendor: Siemens
• Equipment: SIMATIC S7-1200 Devices
• Vulnerability: Improper Authentication

2. UPDATE INFORMATION

This updated advisory is a follow-up to the original advisory titled ICSA-21-222-09 Siemens SIMATIC S7-1200 that was published August 10, 2021, to the ICS webpage on us-cert.cisa.gov.

3. RISK EVALUATION

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Successful exploitation of this vulnerability could allow an attacker using TIA Portal v13 or later versions to bypass authentication and download arbitrary programs to the PLC.

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4. TECHNICAL DETAILS

4.1 AFFECTED PRODUCTS

The following versions of SIMATIC are affected:

• S7-1200 CPU family (incl. SIPLUS variants): Version 4.5.0

4.2 VULNERABILITY OVERVIEW

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4.2.1    IMPROPER AUTHENTICATION CWE-287

Affected devices fail to authenticate against configured passwords when provisioned using TIA Portal v13. This could allow an attacker using TIA Portal v13 or later versions to bypass authentication and download arbitrary programs to the PLC. The vulnerability does not occur when TIA Portal v13 SP1 or a later version was used to provision the device.

CVE-2021-37172 has been assigned to this vulnerability. A CVSS v3 base score of 8.1 has been calculated; the CVSS vector string is (AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H).

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4.3 BACKGROUND

• CRITICAL INFRASTRUCTURE SECTORS: Multiple
• COUNTRIES/AREAS DEPLOYED: Worldwide
• COMPANY HEADQUARTERS LOCATION: Germany

4.4 RESEARCHER

Jian Gao reported this vulnerability to Siemens.

5. MITIGATIONS

Siemens has released updates for the following products:

• S7-1200 CPU family (incl. SIPLUS variants): Update to v4.5.1 or later version

Siemens has identified the following specific workarounds and mitigations users can apply to reduce the risk:

• Update to TIA Portal v13 SP1 or any later version before provisioning S7-1200 v4.5.0 devices.

As a general security measure, Siemens strongly recommends users protect network access to devices with appropriate mechanisms. In order to operate the devices in a protected IT environment, Siemens recommends users configure the environment according to Siemens’ operational guidelines for industrial security and follow the recommendations in the product manuals.

Additional information on industrial security by Siemens can be found at: https://www.siemens.com/industrialsecurity

For more information about this issue, please see Siemens Security Advisory SSA-830194

CISA recommends 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 VPNs may have vulnerabilities and should be updated to the most current version available. Also recognize VPN is only as secure as its connected devices.

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



CISA also provides a section for control systems security recommended practices on the ICS webpage on us-cert.cisa.gov. 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 on the ICS webpage on us-cert.cisa.gov in the Technical Information Paper, ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation Strategies.



Organizations observing any suspected malicious activity should follow their established internal procedures and report their findings to CISA for tracking and correlation against other incidents.

No known public exploits specifically target this vulnerability. This vulnerability has a high attack complexity.