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             AUSCERT External Security Bulletin Redistribution

                      Schneider Electric Modicon PLCs
                               3 April 2017


        AusCERT Security Bulletin Summary

Product:           Schneider Electric Modicon PLCs
Publisher:         ICS-CERT
Operating System:  Network Appliance
Impact/Access:     Denial of Service              -- Remote/Unauthenticated
                   Provide Misleading Information -- Remote/Unauthenticated
                   Unauthorised Access            -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2017-6030 CVE-2017-6028 CVE-2017-6026

Original Bulletin: 

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Advisory (ICSA-17-089-02)

Schneider Electric Modicon PLCs

Original release date: March 30, 2017

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CVSS v3 7.5

ATTENTION: Remotely exploitable/low skill level to exploit.

Vendor: Schneider Electric

Equipment: Modicon PLCs

Vulnerability: Predictable Value Range from Previous Values, Use of
Insufficiently Random Values, Insufficiently Protected Credentials


The following versions of the Modicon M221, M241, and M251 programmable
logic controllers (PLCs) are affected by a predictable value range from
previous values vulnerability:

    Modicon M221, firmware versions prior to Version,
    Modicon M241, firmware versions prior to Version, and
    Modicon M251, firmware versions prior to Version

The following versions of the Modicon M241 and M251 PLCs are affected by
a use of insufficiently random values vulnerability:

    Modicon M241, firmware versions prior to Version, and
    Modicon M251, firmware versions prior to Version

The following versions of the Modicon M241 and M251 PLCs are affected by
an insufficiently protected credentials vulnerability:

    Modicon M241, all firmware versions, and
    Modicon M251, all firmware versions.


Successful exploitation of these vulnerabilities may allow a remote attacker
to spoof or disrupt Transmission Control Protocol (TCP) connections,
sniff sensitive account information, and gain unauthorized access to a
current web session.


Schneider Electric has released new firmware versions to address the
predictable value range from previous values vulnerability and the use of
insufficiently random values vulnerability, which are available through
Schneider Electrics software update tool, SoMachine, Version 4.2,
and SoMachineBasic, Version 1.5. Schneider Electric has not released a
product to address the insufficiently protected credentials vulnerability;
however, Schneider Electric has provided compensating controls to reduce
the risk of exploitation.

SoMachineBasic, Version 1.5, is available at the following location:


Schneider Electric has provided the following compensating controls to
reduce the risk of exploitation of the insufficiently protected credentials

    Verify that the hardware and software infrastructure that the PLCs
    are integrated into (along with all organizational measures and
    rules covering access to the infrastructure) consider the results of
    the hazard and risk analysis, and are implemented according to best
    practices and standards such as ISA/IEC 62443.
    Limit traffic on the local network with managed switches
    Where possible, avoid using Wi-Fi networks, but when Wi-Fi is essential,
    use only secure communications (such as WPA2 encryption)
    Do not grant [network] access to unknown computers
    When remote access is essential, use secure methods such as Virtual
    Private Networks (VPNs), and ensure the remote access solution(s),
    as well as the remote computer(s) are kept up-to-date with the latest
    security patches.

Schneider Electric has released Security Notifications SEVD-2017-075-01,
SEVD-2017-075-02, and SEVD-2017-075-03, which provide additional information
about the identified vulnerabilities, mitigations, and compensating controls:




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.



The affected products generate insufficiently random TCP initial sequence
numbers that may allow an attacker to predict the numbers from previous
values. This may allow an attacker to spoof or disrupt TCP connections.

CVE-2017-6030 has been assigned to this vulnerability. A CVSS v3
base score of 6.5 has been assigned; the CVSS vector string is


The session numbers generated by the web application are lacking
randomization and are shared between several users. This may allow a
current session to be compromised.

CVE-2017-6026 has been assigned to this vulnerability. A CVSS v3
base score of 6.5 has been assigned; the CVSS vector string is


Log-in credentials are sent over the network with Base64 encoding leaving
them susceptible to sniffing. Sniffed credentials could then be used to
log into the web application.

CVE-2017-6028 has been assigned to this vulnerability. A CVSS v3
base score of 7.5 has been assigned; the CVSS vector string is


David Formby and Raheem Beyah of Georgia Tech and Fortiphyd Logic,
Inc. reported the identified vulnerabilities.


Critical Infrastructure Sector(s): Critical Manufacturing, Food and
Agriculture, Water and Wastewater Systems

Countries/Areas Deployed: Worldwide

Company Headquarters Location: Paris, France

Contact Information

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

Email: ics-cert@hq.dhs.gov
Toll Free: 1-877-776-7585
International Callers: (208) 526-0900

For industrial control systems security information and incident reporting:

ICS-CERT continuously strives to improve its products and services. You
can help by choosing one of the links below to provide feedback about
this product.

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