Security readout for executives and security teams
Plain-English summary
CVE-2021-21869 is a high-severity unsafe deserialization issue in CODESYS Development System 3.5.16 and 3.5.17. A malicious file supplied to a user can cause arbitrary command execution when processed. The main business risk is compromise of engineering workstations, with user interaction required.
Executive priority
Treat as a priority for operational technology and engineering teams. The issue requires user interaction, but arbitrary command execution on development systems can create serious downstream operational risk.
Technical view
The affected component is Engine.plugin ProfileInformation ProfileData in CODESYS Development System. Sources classify it as CWE-502 unsafe deserialization with CVSS 8.8. The vector shows no privileges required and user interaction required. Successful exploitation can affect confidentiality, integrity, and availability.
Likely exposure
Exposure is likely limited to environments using CODESYS Development System 3.5.16 or 3.5.17, especially engineering workstations that handle project or profile-related files from external sources.
Exploitation context
The bundle says an attacker can provide a specially crafted file to trigger arbitrary command execution. It does not show CISA KEV listing or other evidence of active exploitation.
Researcher notes
Evidence supports affected versions, vulnerable component, impact, CVSS vector, and user-interaction requirement. The provided bundle does not include exploit prevalence, patch version details, or validated compensating controls.
Mitigation direction
- Inventory CODESYS Development System installations and versions.
- Check the CODESYS advisory for supported fixed versions or vendor mitigations.
- Do not open unsolicited or untrusted CODESYS-related files.
- Restrict external file transfer paths to engineering workstations.
- Apply endpoint controls and monitoring on engineering systems.
Validation and detection
- Confirm whether versions 3.5.16 or 3.5.17 are installed.
- Identify users who process external CODESYS files.
- Review endpoint alerts for suspicious execution from CODESYS tooling.
- Verify vendor guidance has been applied where affected versions exist.
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-502: Code execution behavior lookup
Code execution and unsafe deserialization weaknesses often justify reviewing execution behavior and process telemetry. 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-2021-21869 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
- 8.8 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/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:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H2.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
8.8HighVector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://customers.codesys.com/index.php?eID=dumpFile&t=f&f=16805&token=ee583c498941d9fda86490bca98ff21928eec08a&download=CVE reference · x_refsource_MISC
- https://talosintelligence.com/vulnerability_reports/TALOS-2021-1306CVE reference · 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.
Deserialization of Untrusted Data
Deserialization of Untrusted Data represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.