ESB-2017.2188.2 - UPDATE [Win][Appliance] Various SIMATIC Products: Denial of service - Remote/unauthenticated 2017-10-04

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             AUSCERT External Security Bulletin Redistribution

                              ESB-2017.2188.2
 Advisory (ICSA-17-243-01) Siemens industrial products using the Discovery
        Service of the OPC UA protocol stack by the OPC foundation
                              4 October 2017

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           SIMATIC PCS 7
                   SIMATIC WinCC
                   SIMATIC NET PC Software
                   SIMATIC IT Production Suite
Publisher:         ICS-CERT
Operating System:  Windows
                   Network Appliance
Impact/Access:     Denial of Service        -- Remote/Unauthenticated
                   Access Confidential Data -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2017-12069  

Original Bulletin: 
   https://ics-cert.us-cert.gov/advisories/ICSA-17-243-01

Revision History:  October   4 2017: Updated Product and Mitigation
                   September 1 2017: Initial Release

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Advisory (ICSA-17-243-01A)

Siemens Industrial products using the Discovery Service of the OPC UA protocol
stack by the OPC foundation

Original release date: October 03, 2017

Legal Notice

All information products included in http://ics-cert.us-cert.gov are provided
"as is" for informational purposes only. The Department of Homeland Security 
(DHS) does not provide any warranties of any kind regarding any information 
contained within. DHS does not endorse any commercial product or service, 
referenced in this product or otherwise. Further dissemination of this product
is governed by the Traffic Light Protocol (TLP) marking in the header. For 
more information about TLP, see http://www.us-cert.gov/tlp/.

CVSS v3 8.2

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

UPDATE INFORMATION

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.

AFFECTED PRODUCTS

- --------- Begin Update A Part 1 of 2 --------

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: All versions prior to V6.5

- --------- End Update A Part 1 of 2 --------

IMPACT

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

MITIGATION

- --------- Begin Update A Part 2 of 2 --------

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

SIMATIC PCS 7:
    All affected versions: Follow FAQ:

https://support.industry.siemens.com/cs/ww/en/view/109749461 (link is 
external)

SIMATIC WinCC:
    All versions: Follow FAQ to turn off the service after commissioning:

https://support.industry.siemens.com/cs/ww/en/view/109749461 (link is 
external)

SIMATIC WinCC Runtime Professional:
    Update to V14 SP1

https://support.industry.siemens.com/cs/ww/en/view/109746276 (link is 
external)

All other versions: Follow FAQ to turn off the service after 
commissioning:

https://support.industry.siemens.com/cs/ww/en/view/109749461 (link is 
external)

SIMATIC NET PC Software:
    Follow FAQ to turn off the service after commissioning:

https://support.industry.siemens.com/cs/ww/en/view/109749461 (link is 
external)

- --------- End Update A Part 2 of 2 --------

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:

https://www.siemens.com/cert/operational-guidelines-industrial-security (link
is external)

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 (link is external)

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

https://opcfoundation-onlineapplications.org/faq/SecurityBulletins/OPC_Foundation_Security_Bulletin_CVE-2017-12069.pdf

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 ICSCERT 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.

VULNERABILITY OVERVIEW

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 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).

RESEARCHER

Sergey Temnikov of Kaspersky Lab reported this vulnerability to Siemens.

BACKGROUND

Critical Infrastructure Sectors: Chemical, Energy, Food and Agriculture, Water
and Wastewater Systems

Countries/Areas Deployed: Worldwide

Company Headquarters Location: Germany

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