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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
Publisher:         ICS-CERT
Operating System:  Network Appliance
Impact/Access:     Modify Arbitrary Files         -- Remote/Unauthenticated
                   Provide Misleading Information -- Remote/Unauthenticated
Resolution:        Mitigation
CVE Names:         CVE-2017-6873 CVE-2017-6872 

Original Bulletin: 

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Advisory (ICSA-17-187-01)

Siemens OZW672 and OZW772

Original release date: July 06, 2017

Legal Notice

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CVSS v3 7.4

ATTENTION: Remotely exploitable/low skill level to exploit.

Vendor: Siemens

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.



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 


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

Contact Information

For any questions related to this report, please contact ICS-CERT at:

Email: ics-cert@hq.dhs.gov (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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