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AUSCERT External Security Bulletin Redistribution
ICS Advisory (ICSA-21-047-02)
17 February 2021
AusCERT Security Bulletin Summary
Product: Rockwell Automation Allen-Bradley Micrologix 1100
Operating System: Network Appliance
Impact/Access: Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2020-6111
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ICS Advisory (ICSA-21-047-02)
Rockwell Automation Allen-Bradley Micrologix 1100
Original release date: February 16, 2021
All information products included in https://us-cert.cisa.gov/ics are provided
"as is" for informational purposes only. The Department of Homeland Security
(DHS) does not provide any warranties of any kind regarding any information
contained within. DHS does not endorse any commercial product or service,
referenced in this product or otherwise. Further dissemination of this product
is governed by the Traffic Light Protocol (TLP) marking in the header. For more
information about TLP, see https://us-cert.cisa.gov/tlp/ .
1. EXECUTIVE SUMMARY
o CVSS v3 7.5
o ATTENTION: Exploitable remotely/low skill level to exploit
o Vendor: Rockwell Automation
o Equipment: Allen-Bradley MicroLogix 1100
o Vulnerability: Improper Handling of Length Parameter Inconsistency
2. RISK EVALUATION
Successful exploitation of this vulnerability could result in denial-of-service
3. TECHNICAL DETAILS
3.1 AFFECTED PRODUCTS
Rockwell Automation reports the vulnerability affects the following
Allen-Bradley MicroLogix 1100 Programmable Logic Controller:
o Allen-Bradley MicroLogix 1100 revision number 1.0
3.2 VULNERABILITY OVERVIEW
3.2.1 IMPROPER HANDLING OF LENGTH PARAMETER INCONSISTENCY CWE-130
A vulnerability exists with the processing of ICMP packets with an invalid IPv4
length in the MicroLogix 1100. This vulnerability could allow a remote,
unauthenticated attacker to send malformed packets and cause the controller to
enter 8H Hard Fault. This event would lead to denial-of-service conditions. To
recover from the condition, the controller must be power cycled and the project
CVE-2020-6111 has been assigned to this vulnerability. A CVSS v3 base score of
7.5 has been calculated; the CVSS vector string is ( AV:N/AC:L/PR:N/UI:N/S:U/
o CRITICAL INFRASTRUCTURE SECTORS: Critical Manufacturing
o COUNTRIES/AREAS DEPLOYED: Worldwide
o COMPANY HEADQUARTERS LOCATION: United States
Cisco Talos team reported this vulnerability to Rockwell Automation.
Rockwell Automation recommends users of MicroLogix 1100 migrate to MicroLogix
1400 and apply firmware v21.006 or later .
Please see Rockwell Automation's publication number, PN1548 , for more
Rockwell Automation recommends the following network-based vulnerability
mitigations for embedded products:
o Utilize proper network infrastructure controls, such as firewalls, to help
ensure traffic from unauthorized sources is blocked.
o Consult the product documentation for specific features, such as a hardware
key mode setting, to which may be used to block unauthorized changes, etc.
o Block all traffic to EtherNet/IP or other CIP protocol-based devices from
outside the manufacturing zone by blocking or restricting access to TCP and
UDP Port 2222 and Port 44818 using proper network infrastructure controls,
such as firewalls, UTM devices, or other security appliances. For more
information on TCP/UDP ports used by Rockwell Automation products, see
Knowledgebase Article ID BF7490
Rockwell Automation also recommends the following general mitigations:
o Minimize network exposure for all control system devices and/or systems and
ensure they are not accessible from the Internet. For further information
about the risks of unprotected Internet accessible control systems, please
see Knowledgebase Article ID PN715
o Locate control system networks and devices behind firewalls and isolate
them from the business network.
o 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 a VPN is
only as secure as the connected devices.
CISA recommends users take defensive measures to minimize the risk of
exploitation of this vulnerability. CISA reminds organizations to perform
proper impact analysis and risk assessment prior to deploying defensive
CISA also provides a section for control systems security recommended practices
on the ICS webpage on us-cert.cisa.gov . 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
on the ICS webpage on us-cert.cisa.gov in the Technical Information Paper,
ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation
Organizations observing any suspected malicious activity should follow their
established internal procedures and report their findings to CISA for tracking
and correlation against other incidents.
No known public exploits specifically target this vulnerability.
For any questions related to this report, please contact the CISA at:
Toll Free: 1-888-282-0870
CISA 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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