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Vulnerability record · CVE-2021-22659 · published 25 March 2021

CVE-2021-22659: Rockwellautomation micrologix 1400 firmware classic buffer overflow vulnerability

Rockwellautomation · Micrologix 1400 Firmware

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.

8.6 CVSS 3.1 High EPSS 1.7% · top 23.3% CWE-120 · Classic buffer overflow
8.6CVSS 3.1 base score, v2 7.5
1.7%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References
17 Jun 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://rockwellautomation.custhelp.com/app/answers/answer_view/a_id/1129877/loc/en_US#__highlight Permissions RequiredVendor Advisory
https://us-cert.cisa.gov/ics/advisories/icsa-21-033-01 Third Party AdvisoryUS Government Resource
https://rockwellautomation.custhelp.com/app/answers/answer_view/a_id/1129877/loc/en_US#__highlight Permissions RequiredVendor Advisory
https://us-cert.cisa.gov/ics/advisories/icsa-21-033-01 Third Party AdvisoryUS Government Resource

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2021-22659), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.