Mitsubishi Electric MELSEC iQ-R Series Uncontrolled Resource Consumption (CVE-2021-20591)

high Tenable OT Security Plugin ID 500585

Synopsis

The remote OT asset is affected by a vulnerability.

Description

Uncontrolled Resource Consumption vulnerability in Mitsubishi Electric MELSEC iQ-R series CPU modules (R00/01/02CPU all versions, R04/08/16/32/120(EN)CPU all versions, R08/16/32/120SFCPU all versions, R08/16/32/120PCPU all versions, R08/16/32/120PSFCPU all versions) allows a remote unauthenticated attacker to prevent legitimate clients from connecting to the MELSOFT transmission port (TCP/IP) by not closing a connection properly, which may lead to a denial of service (DoS) condition.

This plugin only works with Tenable.ot. Please visit https://www.tenable.com/products/tenable-ot for more information.

Solution

The following text was originally created by the Cybersecurity and Infrastructure Security Agency (CISA). The original can be found at CISA.gov.

Mitsubishi Electric recommends the following mitigations:

- Use a firewall, a virtual private network (VPN), etc., to prevent unauthorized access when Internet access is required.
- Use within a LAN and block access from untrusted networks and hosts through firewalls.
- 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.
- Use the MELSOFT transmission port (UDP/IP).
- 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.

Plugin Details

Severity: High

ID: 500585

Version: 1.9

Type: remote

Family: Tenable.ot

Published: 2/7/2022

Updated: 9/4/2024

Supported Sensors: Tenable OT Security

Risk Information

VPR

Risk Factor: Low

Score: 3.6

CVSS v2

Risk Factor: High

Base Score: 7.8

Temporal Score: 5.8

Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:C

CVSS Score Source: CVE-2021-20591

CVSS v3

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.5

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/o:mitsubishielectric:r02cpu_firmware, cpe:/o:mitsubishielectric:r32pcpu_firmware, cpe:/o:mitsubishielectric:r08pcpu_firmware, cpe:/o:mitsubishielectric:r00cpu_firmware, cpe:/o:mitsubishielectric:r32psfcpu_firmware, cpe:/o:mitsubishielectric:r120cpu_firmware, cpe:/o:mitsubishielectric:r01cpu_firmware, cpe:/o:mitsubishielectric:r16psfcpu_firmware, cpe:/o:mitsubishielectric:r16pcpu_firmware, cpe:/o:mitsubishielectric:r08psfcpu_firmware, cpe:/o:mitsubishielectric:r16sfcpu_firmware, cpe:/o:mitsubishielectric:r32cpu_firmware, cpe:/o:mitsubishielectric:r120sfcpu_firmware, cpe:/o:mitsubishielectric:r120psfcpu_firmware, cpe:/o:mitsubishielectric:r16cpu_firmware, cpe:/o:mitsubishielectric:r32sfcpu_firmware, cpe:/o:mitsubishielectric:r08sfcpu_firmware, cpe:/o:mitsubishielectric:r08cpu_firmware, cpe:/o:mitsubishielectric:r120pcpu_firmware, cpe:/o:mitsubishielectric:r04cpu_firmware

Required KB Items: Tenable.ot/Mitsubishi

Exploit Ease: No known exploits are available

Patch Publication Date: 6/11/2021

Vulnerability Publication Date: 6/11/2021

Reference Information

CVE: CVE-2021-20591

CWE: 400

ICSA: 21-147-05

Detections

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