Security readout for executives and security teams
Plain-English summary
CVE-2021-33012 can make Rockwell Automation MicroLogix 1100 PLCs fault instead of running. A remote attacker does not need authentication if they can reach the controller. The business concern is availability: affected equipment may be unable to resume RUN mode until the condition is addressed.
Executive priority
Treat this as a high-priority OT availability risk where MicroLogix 1100 controllers support production or critical processes. Prioritize network exposure reduction and vendor-guidance review over broad emergency action unless affected controllers are reachable from untrusted networks.
Technical view
The issue affects Rockwell Automation MicroLogix 1100, all versions. It is classified as CWE-20 improper input validation with CVSS 3.1 score 7.5. A network-reachable, unauthenticated attacker can send crafted commands that cause the PLC to fault when switched to RUN mode, creating denial of service.
Likely exposure
Exposure is most likely in OT environments using MicroLogix 1100 controllers on reachable plant, engineering, or remote-access networks. The provided sources do not show how common internet exposure is or whether other MicroLogix models are affected.
Exploitation context
The bundle does not indicate CISA KEV listing or active exploitation. Exploitability is still concerning because the CVSS vector requires network access, low complexity, no privileges, and no user interaction, but no public exploit status is established here.
Researcher notes
Evidence is limited to the CVE description and CISA advisory reference. The affected scope is stated as MicroLogix 1100 all versions. No patch, workaround, exploit-in-the-wild evidence, or deeper root-cause detail is included in the supplied bundle.
Mitigation direction
- Check CISA and Rockwell guidance for current remediation or replacement direction.
- Identify and prioritize MicroLogix 1100 controllers in production environments.
- Restrict controller reachability to required OT and engineering systems only.
- Review remote-access paths that can reach PLC management interfaces.
- Prepare operational recovery procedures for controller fault conditions.
Validation and detection
- Inventory MicroLogix 1100 assets and record firmware or lifecycle status.
- Confirm whether controllers are reachable from non-OT or remote networks.
- Review logs and incident records for unexplained RUN-mode fault events.
- Validate segmentation rules against approved engineering workstation paths.
- Track vendor advisory updates for named fixes or mitigations.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
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ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-20: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-33012 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://us-cert.cisa.gov/ics/advisories/icsa-21-189-01CVE reference, icscert · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.