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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2021.1835 Advisory (icsa-21-147-05) Mitsubishi Electric MELSEC iQ-R Series 28 May 2021 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: MELSEC iQ-R Series Products Publisher: ICS-CERT Operating System: Network Appliance Impact/Access: Denial of Service -- Remote/Unauthenticated Resolution: Patch/Upgrade CVE Names: CVE-2021-20591 Original Bulletin: https://us-cert.cisa.gov/ics/advisories/icsa-21-147-05 - --------------------------BEGIN INCLUDED TEXT-------------------- ICS Advisory (ICSA-21-147-05) Mitsubishi Electric MELSEC iQ-R Series Original release date: May 27, 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 5.3 o ATTENTION: Exploitable remotely/low attack complexity o Vendor: Mitsubishi Electric o Equipment: MELSEC iQ-R Series o Vulnerability: Uncontrolled Resource Consumption 2. RISK EVALUATION Successful exploitation of this vulnerability may prevent legitimate clients from connecting to an affected product. 3. TECHNICAL DETAILS 3.1 AFFECTED PRODUCTS The following MELSEC iQ-R series CPU modules are affected: o R00/01/02CPU: All versions o R04/08/16/32/120(EN)CPU: All versions o R08/16/32/120SFCPU: All versions o R08/16/32/120PCPU: All versions o R08/16/32/120PSFCPU: All versions 3.2 VULNERABILITY OVERVIEW 3.2.1 UNCONTROLLED RESOURCE CONSUMPTION CWE-400 Due to improper session management, an attacker may prevent legitimate clients from connecting to an affected product by manipulating the link parameter or changing its state. If multiple MELSOFT transmission ports (TCP/IP) are open, the other ports are not affected. Sequence control is not affected by this vulnerability. CVE-2021-20591 has been assigned to this vulnerability. A CVSS v3 base score of 5.3 has been calculated; the CVSS vector string is ( AV:N/AC:L/PR:N/UI:N/S:U/ C:N/I:N/A:L ). 3.3 BACKGROUND o CRITICAL INFRASTRUCTURE SECTORS: Critical Manufacturing o COUNTRIES/AREAS DEPLOYED: Worldwide o COMPANY HEADQUARTERS LOCATION: Japan 3.4 RESEARCHER Younes Dragoni of Nozomi Networks reported this vulnerability to CISA. 4. MITIGATIONS Mitsubishi Electric recommends the following mitigations: o Use a firewall, a 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. o Use the IP filter function to restrict the connectable IP addresses. See MELSEC iQ-R Ethernet User's Manual (Application) 1.13 Security "IP filter" for more information. o Use the MELSOFT transmission port (UDP/IP). o If Port 5007 of the MELSOFT transmission port (TCP/IP) is not used, set b2 to "1" in advance. See MELSEC iQ-R Ethernet User's Manual (Application) Appendix 3, Buffer Memory for more information. If this vulnerability is exploited, legitimate users can recover by first disabling the port with the forced connection invalidation function and then re-enabling the port. For an example see MELSEC iQ-R Ethernet User's Manual (Application) Appendix 3, Buffer Memory. Please refer to the Mitsubishi Electric advisory for further details. 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. No known public exploits specifically target this vulnerability. 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. - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AusCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: https://www.auscert.org.au/bulletins/ =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). 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