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             AUSCERT External Security Bulletin Redistribution

  Download of Code without Integrity Check in Siemens LOGO! Soft Comfort
                             20 December 2017


        AusCERT Security Bulletin Summary

Product:           LOGO! Soft Comfort
Publisher:         Siemens
Operating System:  Network Appliance
Impact/Access:     Reduced Security -- Remote/Unauthenticated
Resolution:        Mitigation
CVE Names:         CVE-2017-12740  

Original Bulletin: 

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ATTENTION: Remotely exploitable.

Vendor: Siemens

Equipment: LOGO! Soft Comfort

Vulnerability: Download of Code without Integrity Check


Siemens reports that the vulnerability affects the following LOGO! Soft Comfort
engineering software products:

  * LOGO! Soft Comfort: All versions prior to V8.2


Successful exploitation of this vulnerability could allow a remote attacker in
a privileged network position to manipulate a software package during download.


Siemens removed the Update Center from LOGO! Soft Comfort V8.2 and provides
SHA-256 checksums for all LOGO! Soft Comfort software packages via a secured
HTTPS channel. Siemens recommends verifying legitimacy by comparing the SHA-256
checksum of the downloaded software package with the SHA-256 checksum provided
for the software package.  Software version 8.2 for LOGO! Soft Comfort and
SHA-256 checksums for LOGO! Soft Comfort downloads can be obtained via:


As a general security measure, Siemens strongly recommends protecting network
access to the devices with appropriate mechanisms. Siemens advises configuring
the environment according to Siemens operational guidelines in order to run the
devices in a protected IT environment.


For more information on this vulnerability and more detailed mitigation
instructions, please see Siemens Security Advisory SSA-888929 at the following


NCCIC/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.

In addition, ICS-CERT recommends that users take the following measures to
protect themselves from social engineering attacks:

 1. Do not click web links or open unsolicited attachments in email messages.
 2. Refer to Recognizing and Avoiding Email Scams for more information on
    avoiding email scams.
 3. Refer to Avoiding Social Engineering and Phishing Attacks for more
    information on social engineering attacks.

No known public exploits specifically target this vulnerability. High skill
level is needed to exploit.



The update center of LOGO! Soft Comfort lacks integrity verification on
software packages downloaded via an unprotected communication channel. This
could allow a remote attacker to manipulate the software package while
performing a man-in-the-middle (MitM) attack.

CVE-2017-12740 has been assigned to this vulnerability. A CVSS v3 base score of
5.9 has been calculated; the CVSS vector string is (AV:N/AC:H/PR:N/UI:N/S:U/C:N


Tobias Gebhardt reported this vulnerability to Siemens.


Critical Infrastructure Sectors: Commercial Facilities, Transportation Systems

Countries/Areas Deployed: Worldwide

Company Headquarters Location: Germany

Contact Information

For any questions related to this report, please contact the NCCIC at:

Toll Free: 1-888-282-0870

For industrial control systems cybersecurity information:  http://
or incident reporting:  https://ics-cert.us-cert.gov/Report-Incident?

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