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             AUSCERT External Security Bulletin Redistribution

                               ESB-2021.3345
         Advisory (icsa-21-280-04) Mitsubishi Electric MELSEC iQ-R
                        Series C Controller Module
                              8 October 2021

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           Mitsubishi Electric MELSEC iQ-R Series C Controller Module
Publisher:         ICS-CERT
Operating System:  Network Appliance
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Mitigation
CVE Names:         CVE-2021-20600  

Original Bulletin: 
   https://us-cert.cisa.gov/ics/advisories/icsa-21-280-04

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ICS Advisory (ICSA-21-280-04)

Mitsubishi Electric MELSEC iQ-R Series C Controller Module

Original release date: October 07, 2021

Legal Notice

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 6.8
  o ATTENTION: Exploitable remotely
  o Vendor: Mitsubishi Electric
  o Equipment: MELSEC iQ-R Series C Controller Module R12CCPU-V
  o Vulnerability: Uncontrolled Resource Consumption

2. RISK EVALUATION

Successful exploitation of this vulnerability could prevent the module from
starting up.

3. TECHNICAL DETAILS

3.1 AFFECTED PRODUCTS

The following modules of the MELSEC iQ-R Series C Controller Module are
affected:

  o R12CCPU-V: All versions

3.2 VULNERABILITY OVERVIEW

3.2.1 UNCONTROLLED RESOURCE CONSUMPTION CWE-400

The potential for a denial-of-service condition exists in MELSEC iQ-R series C
Controller Module due to uncontrolled resource consumption caused by an
attacker sending a large number of packets to the module at start up in a short
time.

CVE-2021-20600 has been assigned to this vulnerability. A CVSS v3 base score of
6.8 has been calculated; the CVSS vector string is ( AV:N/AC:H/PR:N/UI:N/S:C/
C:N/I:N/A:H ).

3.3 BACKGROUND

  o CRITICAL INFRASTRUCTURE SECTORS: Critical Manufacturing
  o COUNTRIES/AREAS DEPLOYED: Worldwide
  o COMPANY HEADQUARTERS LOCATION: Japan

3.4 RESEARCHER

Mitsubishi Electric Corporation reported this vulnerability to CISA.

4. MITIGATIONS

If a System WDT error occurs at start up, there is a possibility the C
Controller Module has been attacked. In this case, disconnect the LAN cable of
the module and restart. After confirming the module has started normally, make
a LAN connection.

Regardless of whether the above error occurred, Mitsubishi Electric recommends
users take the following mitigation measures to minimize the risk of exploiting
this vulnerability:

  o Use a firewall or virtual private network (VPN), etc. to prevent
    unauthorized access when Internet access is required.
  o Use within a LAN and block access from untrusted networks and hosts through
    firewalls.

For specific update instructions and additional details see the Mitsubishi
Electric advisory .

CISA recommends users take defensive measures to minimize the risk of
exploitation of this vulnerability. Specifically, users should:

  o Minimize network exposure for all control system devices and/or systems,
    and ensure that they are not accessible from the Internet .
  o Locate control system networks and remote 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 VPNs may have vulnerabilities and should be
    updated to the most current version available. Also recognize VPN is only
    as secure as its connected devices.

CISA reminds organizations to perform proper impact analysis and risk
assessment prior to deploying defensive measures.

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
Strategies .

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.

CISA also recommends users take the following measures to protect themselves
from social engineering attacks:

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

No known public exploits specifically target this vulnerability. This
vulnerability has a high attack complexity.

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

Email: CISAservicedesk@cisa.dhs.gov
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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