How severe is CVE-2021-33012?

CVE-2021-33012 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 none, integrity none, and availability high.

Is CVE-2021-33012 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (78th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-33012?

CVE-2021-33012 affects Rockwellautomation Micrologix 1100 Firmware. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-33012?

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-2021-33012 published?

CVE-2021-33012 was published on 2021-07-09 and last updated on 2026-06-17.

CVE-2021-33012

CVE-2021-33012 is a high-severity vulnerability in Rockwellautomation Micrologix 1100 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-20.

Key facts

Severity: High (CVSS 3.x base score 8.6)
CVSS v2: 5.0
EPSS exploit prediction: 2% (78th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Rockwellautomation Micrologix 1100 Firmware
Published: 2021-07-09
Last modified: 2026-06-17

Description

Rockwell Automation MicroLogix 1100, all versions, allows a remote, unauthenticated attacker sending specially crafted commands to cause the PLC to fault when the controller is switched to RUN mode, which results in a denial-of-service condition. If successfully exploited, this vulnerability will cause the controller to fault whenever the controller is switched to RUN mode.

Frequently asked questions

What is CVE-2021-33012?: Rockwell Automation MicroLogix 1100, all versions, allows a remote, unauthenticated attacker sending specially crafted commands to cause the PLC to fault when the controller is switched to RUN mode, which results in a denial-of-service condition. If successfully exploited, this vulnerability will cause the controller to fault whenever the controller is switched to RUN mode.
How severe is CVE-2021-33012?: CVE-2021-33012 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 none, integrity none, and availability high.
Is CVE-2021-33012 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (78th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-33012?: CVE-2021-33012 affects Rockwellautomation Micrologix 1100 Firmware. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-33012?: 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-2021-33012 published?: CVE-2021-33012 was published on 2021-07-09 and last updated on 2026-06-17.

References

https://us-cert.cisa.gov/ics/advisories/icsa-21-189-01

Affected products (1)

cpe:2.3:o:rockwellautomation:micrologix_1100_firmware:*:*:*:*:*:*:*:*

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