How severe is CVE-2021-22659?

CVE-2021-22659 has a CVSS 3.x base score of 8.6, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability high.

Is CVE-2021-22659 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (75th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-22659?

CVE-2021-22659 affects Rockwellautomation Micrologix 1400 Firmware. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-22659?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-22659 published?

CVE-2021-22659 was published on 2021-03-25 and last updated on 2026-06-17.

CVE-2021-22659

CVE-2021-22659 is a high-severity vulnerability in Rockwellautomation Micrologix 1400 Firmware with a CVSS 3.x base score of 8.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-120.

Key facts

Severity: High (CVSS 3.x base score 8.6)
CVSS v2: 7.5
EPSS exploit prediction: 2% (75th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-120
Affected product: Rockwellautomation Micrologix 1400 Firmware
Published: 2021-03-25
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-22659?: 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.
How severe is CVE-2021-22659?: CVE-2021-22659 has a CVSS 3.x base score of 8.6, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability high.
Is CVE-2021-22659 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (75th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-22659?: CVE-2021-22659 affects Rockwellautomation Micrologix 1400 Firmware. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-22659?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-22659 published?: CVE-2021-22659 was published on 2021-03-25 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:o:rockwellautomation:micrologix_1400_firmware:*:*:*:*:*:*:*:*

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CVE-2022-3166 — High (CVSS 7.5): Rockwell Automation was made aware that the webservers of the Micrologix 1100 and 1400 controllers contain a…
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