Security readout for executives and security teams
Plain-English summary
This issue affects many Mitsubishi Electric FA engineering tools used around industrial control systems. A remote unauthenticated attacker spoofing expected industrial devices could crash the software on an engineer's PC. The sources also mention possible code execution, but say it was not reproduced.
Executive priority
Treat this as a high-priority OT workstation risk. The most supported impact is loss of engineering software availability, which can disrupt maintenance or response activities. Prioritize inventory, segmentation, and vendor-guided updates.
Technical view
CVE-2021-20588 is CWE-130 improper handling of length parameter inconsistency in Mitsubishi Electric FA Engineering Software. Crafted reply packets spoofing MELSEC, GOT, or FREQROL can trigger denial of service in affected client software. CVSS v3.1 is 7.5, network, low complexity, no privileges or user interaction.
Likely exposure
Exposure is likely on engineering workstations running affected Mitsubishi Electric tools, especially GX Works, GX Developer, GT Designer, configurators, monitoring tools, and related MELSOFT components connected to industrial networks.
Exploitation context
The bundled sources support remote unauthenticated denial of service. They do not support active exploitation; KEV is false. Possible malicious code execution is mentioned, but the CVE description says it has not been reproduced.
Researcher notes
The evidence points to malformed length handling in reply parsing. Keep analysis focused on client-side handling of spoofed device replies. Do not assume reproducible RCE or public exploitation without additional evidence.
Mitigation direction
- Inventory Mitsubishi Electric FA engineering software versions on engineering workstations.
- Check Mitsubishi Electric advisory 2020-021 for product-specific update guidance.
- Segment engineering workstations from untrusted networks and nonessential industrial traffic.
- Restrict who can send device responses to engineering software hosts.
- Apply vendor-recommended updates or compensating controls where updates are unavailable.
Validation and detection
- Compare installed product names and versions against the affected-version list.
- Identify workstations that communicate with MELSEC, GOT, or FREQROL devices.
- Verify engineering hosts are not reachable from untrusted networks.
- Review CISA and Mitsubishi guidance for current remediation status.
- Document any affected all-version products requiring vendor-specific handling.
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
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
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-130: 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-2021-20588 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.
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:H3.93.6Primary CVE scoreVulnerability 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
Source materials
- CVE List V5 sourceCVE List V5
- https://www.mitsubishielectric.com/psirt/vulnerability/pdf/2020-021_en.pdfCVE reference · vendor-advisory
- https://jvn.jp/vu/JVNVU92330101CVE reference · government-resource
- https://www.cisa.gov/news-events/ics-advisories/icsa-21-049-02CVE reference · government-resource
- https://www.mitsubishielectric.com/en/psirt/vulnerability/pdf/2020-021_en.pdfCVE reference · vendor-advisory, x_transferred
- https://jvn.jp/vu/JVNVU92330101/index.htmlCVE reference · government-resource, x_transferred
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 Handling of Length Parameter Inconsistency
Improper Handling of Length Parameter Inconsistency represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.