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AUSCERT External Security Bulletin Redistribution
Advisory (ICSA-17-187-01) Siemens OZW672 and OZW772
7 July 2017
AusCERT Security Bulletin Summary
Product: Siemens OZW672 and OZW772
Operating System: Network Appliance
Impact/Access: Modify Arbitrary Files -- Remote/Unauthenticated
Provide Misleading Information -- Remote/Unauthenticated
CVE Names: CVE-2017-6873 CVE-2017-6872
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Siemens OZW672 and OZW772
Original release date: July 06, 2017
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
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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 7.4
ATTENTION: Remotely exploitable/low skill level to exploit.
Equipment: OZW672 and OZW772
Vulnerabilities: Missing Authentication
Siemens reports that the vulnerability affects the following OZW672 and OZW772
devices for monitoring building controller devices:
OZW672: All versions, and
OZW772: All versions.
Successful exploitation of this vulnerability could allow attackers to read
and write historical measurement data under certain conditions, or to read and
modify data in TLS sessions.
Siemens recommends applying the following mitigations:
Protect network access to the affected devices.
Disable integrated service on Port 21/TCP in the device settings by changing
the value of ACS access under Settings > Communication > Services to Off.
Applying this configuration change mitigates CVE-2017-6872 entirely.
Use the web portal as described in the product documentation for all
applications; Connections to the web portal are not affected by CVE-2017-6873.
If use of web portal is not possible, then use the integrated web server only
in trusted networks.
For more information on this vulnerability and more detailed mitigation
instructions, please see Siemens Security Advisory SSA-563539 at the following
http://www.siemens.com/cert/advisories (link is external)
NCCIC/ICS-CERT recommends that users take defensive measures to minimize the
risk of exploitation of these vulnerabilities. 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 these vulnerabilities.
MISSING AUTHENTICATION FOR CRITICAL FUNCTION CWE-306
An attacker with access to Port 21/TCP could access or alter historical
measurement data stored on the device.
CVE-2017-6872 has been assigned to this vulnerability. A CVSS v3 base score of
6.5 has been calculated; the CVSS vector string is
MISSING AUTHENTICATION FOR CRITICAL FUNCTION CWE-306
A vulnerability in the integrated web server on Port 443/TCP could allow an
attacker to read and manipulate data in TLS sessions while performing a
man-in-the-middle (MITM) attack.
CVE-2017-6873 has been assigned to this vulnerability. A CVSS v3 base score of
7.4 has been calculated; the CVSS vector string is
Stefan Viehbck from SEC Consult reported these vulnerabilities to Siemens.
Critical Infrastructure Sector: Commercial Facilities
Countries/Areas Deployed: Worldwide
Company Headquarters Location: Germany
For any questions related to this report, please contact ICS-CERT at:
Email: email@example.com (link sends e-mail)
Toll Free: 1-877-776-7585
International Callers: (208) 526-0900
For industrial control systems security information and incident reporting:
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