Siemens industrial products using the Discovery Service of the OPC UA protocol stack by the OPC foundation (Update B)
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CVSS v3 8.2
ATTENTION: Remotely exploitable/low skill level to exploit.
Equipment: Industrial products using the Discovery Service of the OPC UA protocol stack by the OPC foundation
Vulnerability: Improper Restriction of XML External Entity Reference
This updated advisory is a follow-up to the advisory update titled ICSA-17-242-01A Siemens industrial products using the Discovery Service of the OPC UA protocol stack by the OPC foundation that was published October 3, 2017, on the NCCIC/ICS-CERT web site.
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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 PCS 7
- V8.0: All versions
- V8.1: All versions
- SIMATIC WinCC:
- V7.2: All versions
- SIMATIC WinCC Runtime Professional:
- V13: All versions
- V14: All versions prior to V14 SP1
- SIMATIC NET PC Software: All versions
- SIMATIC IT Production Suite: Versions between V6.5 and V7.1
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Successful exploitation of this vulnerability may allow an attacker to access various resources.
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Siemens provides fixes for the following products and recommends users upgrade to the newest version:
- SIMATIC PCS 7:
- All affected versions: Follow FAQ:
- SIMATIC WinCC:
- All versions: Follow FAQ to turn off the service after commissioning:
- SIMATIC WinCC Runtime Professional:
- Update to V14 SP1
- All other versions: Follow FAQ to turn off the service after commissioning:
- SIMATIC NET PC Software:
- Follow FAQ to turn off the service after commissioning:
- SIMATIC IT Production Suite:
- Contact local support to update to V7.1
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Siemens is preparing further updates and recommends the following mitigations in the meantime:
- Turn off the Discovery Service or block it on the local firewall,
- Apply cell protection concept,
- Use VPN for protecting network communication between cells, and
- Apply Defense in Depth.
Siemens recommends users protect network access with appropriate mechanisms such as firewalls, segmentation, and VPNs. 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-535640 at the following location:
The OPC Foundation also published a security bulletin for this vulnerability:
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.
By sending specially crafted packets to the OPC Discovery Server at Port 4840/TCP, an attacker might cause the system to access various resources chosen by the attacker.
Sergey Temnikov of Kaspersky Lab 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
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