Security readout for executives and security teams
Plain-English summary
This issue affects Rockwell Automation MicroLogix 1400 controllers running Version 21.6 and below. A remote attacker who can reach the controller over the relevant network path may cause a denial-of-service condition. The controller may enter fault state, flash the FAULT LED red, and lose communications until a user clears the fault.
Executive priority
Treat this as high priority for industrial environments where affected controllers support production, safety-adjacent, or availability-sensitive operations. The main business risk is operational disruption requiring manual recovery, not confirmed data theft or public exploitation from the supplied evidence.
Technical view
CVE-2021-22659 is a CWE-120 buffer overflow issue in MicroLogix 1400 Version 21.6 and below. The source describes unauthenticated network access with low attack complexity via a specially crafted Modbus packet. Successful exploitation can affect availability, with CVSS 3.1 score 7.5 and vector AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
Likely exposure
Exposure is most relevant where MicroLogix 1400 controllers Version 21.6 or below are reachable by untrusted or insufficiently segmented networks using Modbus. The bundle does not identify affected CPEs or internet exposure prevalence.
Exploitation context
The supplied sources do not state active exploitation, and this CVE is not marked as CISA KEV in the bundle. The described condition is remotely reachable and unauthenticated if network access to the affected controller is available.
Researcher notes
The strongest evidence is the CVE description, CVSS vector, CWE-120 classification, and affected firmware range. The bundle does not include proof-of-concept details, observed exploitation, exact fixed version, or complete vendor mitigation text, so avoid claims beyond Rockwell and CISA guidance.
Mitigation direction
- Inventory MicroLogix 1400 controllers and firmware versions.
- Review Rockwell advisory 1129877 for vendor-approved remediation.
- Review CISA ICSA-21-033-01 for operational mitigations.
- Restrict network access to affected controllers while remediation is planned.
- Prepare procedures to clear controller fault states if service is disrupted.
Validation and detection
- Confirm whether any MicroLogix 1400 devices run Version 21.6 or below.
- Verify Modbus reachability only from authorized control-network paths.
- Check monitoring for unexpected controller fault states or communications loss.
- Document remediation status against Rockwell and CISA guidance.
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-120: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-22659 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
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-21-033-01CVE reference, icscert · x_refsource_MISC
- https://rockwellautomation.custhelp.com/app/answers/answer_view/a_id/1129877/loc/en_US#__highlightCVE 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.
Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.