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Micrologix 1100 Firmware CVE-2021-33012

HIGH
Improper Input Validation (CWE-20)
2021-07-09 ics-cert@hq.dhs.gov
Information Disclosure Rockwell Micrologix 1100 Firmware Rockwellautomation
8.6
CVSS 3.1 · NVD
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Vulnerability Assessment

Weakness
CWE
CWE-20
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V2 - Validation and Business Logic Input validation, allowlisting
Impact

CVSS score of 8.6 (HIGH). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. EPSS exploitation probability: 2.74%.
Exploit ScenarioDerived

This vulnerability can be exploited remotely over the network. Successful exploitation could compromise the high-severity affected system.
This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
No patch listed yet 2.7% exploitation probability (EPSS)

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AnalysisAI

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,. Rated high severity (CVSS 8.6), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

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Technical ContextAI · show details

This vulnerability is classified under CWE-20. 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. Affected products include: Rockwellautomation Micrologix 1100 Firmware.

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  • Exploit and PoC references, threat intelligence from 22 sources
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Severity by source

NVD PRIMARY 8.6 HIGH
AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

DescriptionCVE.org

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.

Threat Intelligence Overview

EPSS Score
2.7%
Top 14% exploitable
Data Quality
4 sources
Confidence: Medium
NVD CVE.org EPSS VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC No
EPSS 2.7%
Patch available No
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
Yes
Human Impact· derived
Medium

Priority Score

46
Low Medium High Critical
KEV: 0
EPSS: +3
CVSS: +43
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

Affected Products (CPE)CVE.org

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

More in Micrologix 1100 Firmware

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CVE-2015-6490 CRITICAL
9.8 Oct 28

Stack-based buffer overflow on Allen-Bradley MicroLogix 1100 devices before B FRN 15.000 and 1400 devices through B FRN

CVE-2020-6990 CRITICAL
9.8 Mar 16

Rockwell Automation MicroLogix 1400 Controllers Series B v21.001 and prior, Series A, all versions, MicroLogix 1100 Cont
CVE-2015-6492 HIGH
7.5 Oct 28

Allen-Bradley MicroLogix 1100 devices before B FRN 15.000 and 1400 devices before B FRN 15.003 allow remote attackers to
CVE-2020-6984 HIGH
7.5 Mar 16

Rockwell Automation MicroLogix 1400 Controllers Series B v21.001 and prior, Series A, all versions, MicroLogix 1100 Cont
CVE-2020-6988 HIGH
7.5 Mar 16

Rockwell Automation MicroLogix 1400 Controllers Series B v21.001 and prior, Series A, all versions, MicroLogix 1100 Cont
CVE-2022-3166 HIGH
7.5 Dec 16

Rockwell Automation was made aware that the webservers of the Micrologix 1100 and 1400 controllers contain a vulnerabili
CVE-2019-10955 MEDIUM
6.1 Apr 25

In Rockwell Automation MicroLogix 1400 Controllers Series A, All Versions Series B, v15.002 and earlier, MicroLogix 1100
CVE-2015-6486 MEDIUM
6.5 Oct 28

SQL injection vulnerability on Allen-Bradley MicroLogix 1100 devices before B FRN 15.000 and 1400 devices before B FRN 1
CVE-2022-2179 MEDIUM
6.5 Jul 20

The X-Frame-Options header in Rockwell Automation MicroLogix 1100/1400 Versions 21.007 and prior is not configured in th
CVE-2022-46670 MEDIUM
6.1 Dec 16

Rockwell Automation was made aware of a vulnerability by a security researcher from Georgia Institute of Technology that
CVE-2015-6488 MEDIUM
4.3 Oct 28

Cross-site scripting (XSS) vulnerability in the web server on Allen-Bradley MicroLogix 1100 devices before B FRN 15.000

CVE-2015-6491 MEDIUM
4.0 Oct 28

Allen-Bradley MicroLogix 1100 devices before B FRN 15.000 and 1400 devices before B FRN 15.003 allow remote authenticate

Same weakness CWE-20 – Improper Input Validation

View all
CVE-2021-44228 CRITICAL POC
10.0
CVE-2024-3400 CRITICAL POC
10.0
CVE-2022-47966 CRITICAL POC
9.8
CVE-2023-22515 CRITICAL POC
9.8
CVE-2009-0927 HIGH POC
8.8
CVE-2017-9791 CRITICAL POC
9.8
CVE-2017-15944 CRITICAL POC
9.8
CVE-2019-0604 CRITICAL POC
9.8

Same technique Information Disclosure

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CVE-2019-2725 CRITICAL POC
9.8
CVE-2021-34523 CRITICAL POC
9.0
CVE-2013-2251 CRITICAL POC
9.8
CVE-2017-5638 CRITICAL POC
9.8
CVE-2025-24813 CRITICAL POC
9.8
CVE-2025-68613 HIGH POC
8.8
CVE-2015-1701 HIGH POC
7.8
CVE-2017-0147 HIGH POC
7.5

References

Advisories & patches
ADVISORY https://vuldb.com/vuln/178205 REF https://us-cert.cisa.gov/ics/advisories/icsa-21-189-01

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