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Rockwell Automation released mitigation strategies to protect against an undocumented and privileged Simple Network Management Protocol (SNMP) community string that exists in MicroLogix 1400 programmable logic controllers (PLC), according to a report with ICS-CERT.

This vulnerability, reported by Cisco Talos, Cisco Systems, Inc.’s security intelligence and research group, is remotely exploitable.

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Rockwell said the vulnerability affects all versions of the following products:
• 1766-L32BWA
• 1766-L32AWA
• 1766-L32BXB
• 1766-L32BWAA
• 1766-L32AWAA
• 1766-L32BXBA

This vulnerability may allow an attacker to make unauthorized changes to the product’s configuration, including firmware updates.

Cyber Security

Rockwell Automation, which is a Milwaukee, WI-based company, provides industrial automation control and information products worldwide across a wide range of industries.

The affected products, MicroLogix, are PLCs. These products see action across several sectors, including chemical, critical manufacturing, food and agriculture, and water and wastewater systems. Rockwell said these products see use in Germany, Czech Republic, France, Poland, Denmark, Hungary, Italy, and other countries in Europe, as well as in the United States, Korea, China, Japan, and in Latin American countries.

SNMP is a standard protocol employed by many types of Internet protocol based products and allows centralized and remote device management capabilities. One of the many standard SNMP capabilities enables users to manage the product’s firmware, including the capability of applying firmware updates to the product. The MicroLogix 1400 utilizes this standard SNMP capability as its official mechanism for applying firmware updates to the product.
CVE-2016-5645 is the case number assigned to this vulnerability, which has a CVSS v3 base score of 7.3.

No known public exploits specifically target this vulnerability. However, an attacker with a low skill would be able to exploit this vulnerability.

Due to the nature of this product’s firmware update process, the user cannot remove this capability from the product. Instead, there are mitigations to reduce risk of this capability falling in the hands of an attacker.

Rockwell Automation recommends users using affected versions of the MicroLogix 1400 evaluate and deploy the risk mitigation strategies listed below. When possible, multiple strategies should be employed simultaneously.

• Utilize the product’s “RUN” keyswitch setting to prevent unauthorized and undesired firmware update operations and other disruptive configuration changes.
• Utilize proper network infrastructure controls, such as firewalls, to help ensure SNMP requests from unauthorized sources are blocked. See KB496391 for more information on blocking access to SNMP services.
• Disable the SNMP service on this product. The SNMP service is enabled by default. See Page 128 in the MicroLogix 1400 product manual for detailed instructions on enabling and disabling SNMP. ( Note: It will be necessary to re-enable SNMP to update firmware on this product. After the upgrade is complete, disable the SNMP service once again. Another note: Changing the SNMP community strings is not an effective mitigation.
• Minimize network exposure for all control system devices and/or systems and ensure they are not accessible from the Internet.
• Locate control system networks and devices behind firewalls, and isolate them from the business network.

When remote access ends up required, use secure methods, such as virtual private networks (VPNs), recognizing that VPNs may have vulnerabilities and should end up updated to the most current version available. Also recognize a VPN is only as secure as the connected devices.

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