Rockwell Automation MicroLogix 1400 Buffer Copy Without Checking Size of Input (CVE-2021-22659)

high Tenable OT Security Plugin ID 500469

Synopsis

The remote OT asset is affected by a vulnerability.

Description

Rockwell Automation MicroLogix 1400 Version 21.6 and below may allow a remote unauthenticated attacker to send a specially crafted Modbus packet allowing the attacker to retrieve or modify random values in the register. If successfully exploited, this may lead to a buffer overflow resulting in a denial-of-service condition. The FAULT LED will flash RED and communications may be lost. Recovery from denial- of-service condition requires the fault to be cleared by the user.

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.

Rockwell Automation recommends users with the affected controller to mitigate risk. They encourage, when possible, to combine this guidance with the general security guidelines for a comprehensive defense-in-depth strategy. Please subscribe to updates to this advisory and the Industrial Security Advisory Index to stay notified.

All users, if applicable, may disable Modbus TCP support if it is not necessary for their MicroLogix 1400 implementation. Without Modbus TCP enabled, a potential attacker does not have access to exploit the device using this vulnerability.

For additional information see Rockwell Automation Security Advisory PN1545.

Rockwell Automation recommends the following network-based vulnerability mitigations for embedded products:

- Utilize proper network infrastructure controls (such as firewalls) to help ensure Modbus TCP from unauthorized sources are blocked.
- Consult the product documentation for specific features (such as a hardware keyswitch setting), which may be used to block unauthorized changes, etc.
- 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 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 898270.

Rockwell Automation recommends the following software/PC-based mitigation strategies:

- Run all software as a User, not as an Administrator, to minimize the impact of malicious code on the infected system.
- Use of Microsoft AppLocker or other similar allow list application can help mitigate risk. Information on using AppLocker with Rockwell Automation products is available at Knowledgebase Article ID 546989.
- Ensure the least-privilege user principle is followed, and user/service account access to shared resources (such as a database) is only granted with a minimum of rights as needed.

Rockwell Automation recommends the following general mitigations:

- Use trusted software, software patches, antivirus/antimalware programs, and interact only with trusted websites and attachments.
- 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 494865.
- Locate control system networks and devices behind firewalls and isolate them from the business network.
- When remote access is required, use secure methods, such as virtual private networks (VPNs), and recognize 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.

Plugin Details

Severity: High

ID: 500469

File Name: tenable_ot_rockwell_CVE-2021-22659.nasl

Version: 1.15

Type: Remote

Family: Tenable.ot

Published: 2/7/2022

Updated: 6/21/2026

Supported Sensors: Tenable OT Security

Risk Information

VPR

Risk Factor: Low

Score: 3.9

Percentile: 52.23

CVSS v2

Risk Factor: High

Base Score: 7.5

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

CVSS Score Source: CVE-2021-22659

CVSS v3

Risk Factor: High

Base Score: 8.6

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

Vulnerability Information

CPE: cpe:/o:rockwellautomation:micrologix_1400_firmware

Required KB Items: Tenable.ot/Rockwell

Exploit Ease: No known exploits are available

Patch Publication Date: 3/25/2021

Vulnerability Publication Date: 3/25/2021

Reference Information

CVE: CVE-2021-22659

CWE: 120

ICSA: 21-033-01

Detections

Analytics