Skip to main content
No exploitation reported

CVE-2021-33012

No exploitation reported by the sources we read.

  • Published2021-07-09
  • WeaknessCWE-20

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2021-07-0915:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-33012?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-33012?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Rockwellautomation micrologix 1100 firmwareversion to verify
BranchAffectedFixed in
—all versionsno fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Vendor advisories

  • ICSA-21-189-01 CISA1 known affected

    Rockwell Automation MicroLogix 1100

    MicroLogix 1100: All versions

Full record on NVD

Fix

  1. Mitigation from the vendor CISA ICSA-21-189-01 · 1 productA controller in this fault state can be recovered by downloading a new project or an offline copy of the project to the controller. Rockwell Automation recommends users set the controller switch to RUN mode to prevent remote programming. Users are encouraged to have a backup copy of the project in …
  2. Mitigation from the vendor CISA ICSA-21-189-01 · 1 productUtilize proper network infrastructure controls, such as firewalls, to help ensure EtherNet/IP traffic from unauthorized sources are blocked.
  3. Mitigation from the vendor CISA ICSA-21-189-01 · 1 productConsult the product documentation for specific features, such as a hardware mode switch setting, to which may be used to block unauthorized changes, etc.
  4. Mitigation from the vendor CISA ICSA-21-189-01 · 1 productBlock 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 Port 44818 using proper network infrastructure controls, such as firewalls, UTM devices, or other security appliances. For more inf…
  5. Mitigation from the vendor CISA ICSA-21-189-01 · 1 productUse trusted software, software patches, antivirus/antimalware programs and interact only with trusted websites and attachments.
  6. Mitigation from the vendor CISA ICSA-21-189-01 · 1 productMinimize 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 PN715

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • CISA-ADPSSVC decisionnone2026-06-03
  • OpenCVESSVC decisionnone—
  • CISA-ADPCVSS 3.17.52026-06-03
  • NVDCVSS 3.18.6read 2026-10-23
  • NVDCVSS 2.05read 2026-10-23
  • CNAweakness (CWE)CWE-20read 2026-10-23
  • FIRST EPSSEPSS score2.6 %2026-10-23

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Published
2021-07-09
Last Modified
2026-06-17
NVD status
Modified

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.

Is CVE-2021-33012 actively exploited?

Active exploitation of CVE-2021-33012 has not been confirmed. Its EPSS score was 2.6% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-33012?

CVE-2021-33012 has a CVSS v3 base score of 8.6 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H.

Running Rockwell Automation MicroLogix? Hear about its next vulnerability

Surveillance reads the versions in your stack — a domain, a lockfile or a list — checks each CVE against the ranges its sources publish, and alerts you when one you run is exploited or enters CISA KEV. A version it cannot read stays « version not verified ».

Get alerts for this productCISA KEV additions, October 2026Search CVEs

No credit card required · No monthly cap on website lookups · 250 API requests/month

Go further

Related vulnerabilities

Same product first, then the same vendor advisory and the same publication week.

Back to CVE Database