**ATTENTION:**Remotely exploitable/low skill level to exploit.
Vendor: Siemens
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 original advisory titled ICSA-17-242-01 Siemens Industrial products using the Discovery Service of the OPC UA protocol stack by the OPC foundation that was published August 31, 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:
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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:
<https://support.industry.siemens.com/cs/ww/en/view/109749461>
<https://support.industry.siemens.com/cs/ww/en/view/109749461>
<https://support.industry.siemens.com/cs/ww/en/view/109746276>
<https://support.industry.siemens.com/cs/ww/en/view/109749461>
<https://support.industry.siemens.com/cs/ww/en/view/109749461>
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Siemens is preparing further updates and recommends the following mitigations in the meantime:
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 Siemensβ Operational Guidelines for Industrial Security:
<https://www.siemens.com/cert/operational-guidelines-industrial-security>
For more information on this vulnerability and more detailed mitigation instructions, please see Siemens Security Advisory SSA-535640 at the following location:
<http://www.siemens.com/cert/advisories>
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:
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 ICSβCERT Technical Information Paper, ICS-TIP-12-146-01BβTargeted 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.
CVE-2017-12069 has been assigned to this vulnerability. A CVSS v3 base score of 8.2 has been assigned; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H).
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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opcfoundation-onlineapplications.org/faq/SecurityBulletins/OPC_Foundation_Security_Bulletin_CVE-2017-12069.pdf
support.industry.siemens.com/cs/ww/en/view/109746276
support.industry.siemens.com/cs/ww/en/view/109749461
support.industry.siemens.com/cs/ww/en/view/109749461
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support.industry.siemens.com/cs/ww/en/view/109749461
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