Siemens OPC UA Protocol Stack Discovery Service (Update E)

1. EXECUTIVE SUMMARY

• CVSS v3 8.2
• ATTENTION: Exploitable remotely/low skill level to exploit
• Vendor: Siemens
• Equipment: SIMATIC
• Vulnerabilities: Improper restriction of XML external entity reference

2.  UPDATE INFORMATION

This updated advisory is a follow-up to the advisory update titled ICSA-17-243-01 Siemens OPC UA Protocol Stack Discovery Service (Update D) that was published August 11, 2020, on the on the ICS webpage on www.cisa.gov/uscert.

3. RISK EVALUATION

Successful exploitation of this vulnerability may allow an attacker to access various resources.

4. TECHNICAL DETAILS

4.1 AFFECTED PRODUCTS

Siemens reports that the vulnerability affects the following industrial products, which use the Discovery Service of the OPC UA protocol stack by the OPC foundation:

• SIMATIC IT Production Suite: Versions between v6.5 and v7.1

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• SIMATIC NET PC Software 14: All versions prior to v14 SP1 Update 14
• SIMATIC PCS 7: Versions v8.0, v8.1
• SIMATIC WinCC: All versions prior to v7.2
• SIMATIC WinCC Runtime Professional v13: All versions
• SIMATIC WinCC Runtime Professional v14: All versions prior to v14 SP1

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4.2 VULNERABILITY OVERVIEW

4.2.1    IMPROPER RESTRICTION OF XML EXTERNAL ENTITY REFERENCE ('XXE') CWE-611

By sending specially crafted packets to the OPC Discovery Server at Port 4840/TCP, an attacker may be able to cause the system to access various resources chosen by the attacker. 

CVE-2017-12069 has been assigned to this vulnerability. A CVSS v3 base score of 8.2 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H).

4.3 BACKGROUND

• CRITICAL INFRASTRUCTURE SECTORS: Chemical, Energy, Food and Agriculture, Water and Wastewater Systems
• COUNTRIES/AREAS DEPLOYED: Worldwide
• COMPANY HEADQUARTERS LOCATION: Germany

4.4 RESEARCHER

Sergey Temnikov of Kaspersky Lab reported this vulnerability to Siemens.

5. MITIGATIONS

Siemens provides fixes for the following products and recommends users upgrade to the newest version:

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• SIMATIC IT Production Suite: Contact local support to update to v7.1
• SIMATIC NET PC Software v14: Update to v14 SP1 Update 14 or later version
• SIMATIC WinCC Runtime Professional v14: Update to v14 SP1 or later version

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

• Turn off the discovery service after commissioning or block it on the local firewall. 
• Use VPN for protecting network communication between cells

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

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

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For more information on this vulnerability and more detailed mitigation instructions, please see Siemens Security Advisory SSA-535640

The OPC Foundation also published a security bulletin for this vulnerability.

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 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 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.