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             AUSCERT External Security Bulletin Redistribution

   Advisory (ICSA-17-101-01) Schneider Electric Modicon Modbus Protocol
                               12 April 2017


        AusCERT Security Bulletin Summary

Product:           Modicon Modbus Protocol
Publisher:         Schneider Electric
Operating System:  Network Appliance
Impact/Access:     Provide Misleading Information -- Remote with User Interaction
Resolution:        Mitigation
CVE Names:         CVE-2017-6034 CVE-2017-6032 

Original Bulletin: 

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Advisory (ICSA-17-101-01)

Schneider Electric Modicon Modbus Protocol

Original release date: April 11, 2017

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CVSS v3 10.0

ATTENTION: Remotely exploitable/low skill level to exploit.

Vendor: Schneider Electric

Equipment: Modicon Modbus Protocol

Vulnerabilities: Authentication Bypass by Capture-Replay, Violation of Secure
Design Principles


The following versions of Modicon Modbus protocol, which can be used with the
Modicon family of programmable logic controllers (PLCs), are affected:

Modicon Modbus protocol, all versions.


Successful exploitation of these vulnerabilities may allow an unauthorized 
remote attacker to capture and replay sensitive commands to PLCs on a network
using the Modicon Modbus protocol.


Schneider Electric has reported that they have introduced compensating 
controls to limit the exploitability of the identified vulnerabilities in many
of the PLCs in the Modicon family; however, Schneider Electric recommends that
users apply security measures to improve resiliency.

Schneider Electric's Momentum M1E controllers (all versions of model 
171CBU98090 and all versions of model 171CBU98091) do not have built-in 
compensating controls to limit the exploitability of the identified 
vulnerabilities and Schneider Electric instructs users to take the following 
defensive measures:

Protect access to M1E controllers by a firewall blocking all remote/external 
access to Port 502.

Schneider Electric reports that Modicon M340, M580, Premium and Quantum users
should take one or more of the following defensive measures:

Enable protection based on an authentication to connect to PLC. This method 
relies on a feature named Application Password. Once enabled, password-based 
authentication is required whenever a user connects to change their 
application program;

Enable protection relying on an input (M340, Premium, Quantum) or a key switch
in the front panel (Quantum) to reject remote connection or run/stop commands;

Enable the "Access Control List protection," where users are able to configure
the restricted IP addresses that are pre-authorized to control the PLC.

For additional information, Schneider Electric has released a Cybersecurity 
Notification, which is available at the following location:

http://www.schneider-electric.com/en/download/document/SEVD-2017-065-01/ (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 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.



Sensitive information is transmitted in cleartext in the Modicon Modbus 
protocol, which may allow an attacker to replay the following commands: run, 
stop, upload, and download.

CVE-2017-6034 has been assigned to this vulnerability. A CVSS v3 base score of
10.0 has been assigned; the CVSS vector string is 


The Modicon Modbus protocol has a session-related weakness making it 
susceptible to brute-force attacks.

CVE-2017-6032 has been assigned to this vulnerability. A CVSS v3 base score of
5.3 has been assigned; the CVSS vector string is 


Eran Goldstein of CRITIFENCE reported the identified vulnerabilities.


Critical Infrastructure Sectors: Critical Manufacturing, Dams, Defense 
Industrial Base, Energy, Food and Agriculture, Government Facilities, Nuclear
Reactors, Materials, and Waste, Transportation Systems, and Water and 
Wastewater Systems

Countries/Areas Deployed: Worldwide

Company Headquarters Location: Paris, France

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