Mitsubishi MELSEC-Q Series C Controller Module Denial of Service and Malicious Code Execution (CVE-2021-29998)

critical Tenable OT Security Plugin ID 501838


The remote OT asset is affected by a vulnerability.


Denial of Service and Malicious Code Execution Vulnerability exists in DHCP client function of VxWorks version 6.4, a real-time OS distributed by Wind River. A remote attacker may cause a denial of service (DoS) condition or execute malicious code on a target product by sending specially crafted packets.

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Mitsubishi Electric recommends the following:

- Update to 24032 (first 5 digits of serial number) or later. Contact a Mitsubishi Electric representative for more information.
- Disable the DHCP function in “Security Settings” of the C language controller settings/monitor tool if the product is in “Extended mode” and the DHCP client function is not required.
- Update DHCP server to the latest version.
- Use a firewall or virtual private network (VPN), etc. to prevent unauthorized access when Internet access is required.
- Use within a trusted LAN that is properly divided by routers and firewalls.

For more information see Mitsubishi Electric’s advisory 2022-001

See Also

Plugin Details

Severity: Critical

ID: 501838

Version: 1.1

Type: remote

Family: Tenable.ot

Published: 12/18/2023

Updated: 12/19/2023

Supported Sensors: Tenable OT Security

Risk Information


Risk Factor: Medium

Score: 5.9


Risk Factor: High

Base Score: 7.5

Temporal Score: 5.5

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

CVSS Score Source: CVE-2021-29998


Risk Factor: Critical

Base Score: 9.8

Temporal Score: 8.5

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

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

Vulnerability Information

CPE: cpe:/o:mitsubishielectric:q12dccpu-v_firmware

Required KB Items: Tenable.ot/Mitsubishi

Exploit Ease: No known exploits are available

Patch Publication Date: 4/13/2021

Vulnerability Publication Date: 4/13/2021

Reference Information

CVE: CVE-2021-29998