CVE-2021-33012

Name: CVE-2021-33012
Creator: NVD / NIST
Published: 2021-07-09T15:15:08.503+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.6/10EPSS 1.95%

Last modified Jun 17, 2026

CVE-2021-33012 is a high-severity vulnerability rated 8.6/10 on the CVSS scale. 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.. EPSS estimates a 1.95% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

8.6/10

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

EPSS Probability

1.95%

77.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-20

Affected Software

Vendor	Product	Versions
Rockwellautomation	Micrologix 1100 Firmware	All versions

References

https://us-cert.cisa.gov/ics/advisories/icsa-21-189-01Third Party Advisory, US Government Resource
https://us-cert.cisa.gov/ics/advisories/icsa-21-189-01Third Party Advisory, US Government Resource

Timeline

Published: Jul 9, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-33012?

How severe is CVE-2021-33012?

CVE-2021-33012 has a CVSS score of 8.6/10 (HIGH severity). The EPSS model estimates a 1.95% probability of exploitation in the next 30 days.

How do I fix CVE-2021-33012?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-33012?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST