Security readout for executives and security teams
Plain-English summary
CVE-2021-21868 affects CODESYS Development System 3.5.16 and 3.5.17. A malicious file opened by a user can trigger unsafe deserialization and allow arbitrary command execution. The business risk is compromise of engineering workstations used to develop or maintain industrial control applications.
Executive priority
Treat this as high priority where CODESYS engineering workstations support operational technology or safety-critical environments. The required user action lowers likelihood, but successful compromise could affect sensitive project files and workstation integrity.
Technical view
The flaw is CWE-502 unsafe deserialization in ObjectManager.plugin Project.get_MissingTypes(). The CVSS 3.0 score is 8.8 with no privileges required, user interaction required, and high confidentiality, integrity, and availability impact.
Likely exposure
Most likely exposed assets are engineering or developer workstations running CODESYS Development System 3.5.16 or 3.5.17. The provided sources do not identify PLC runtime devices or other CODESYS products as affected.
Exploitation context
The sources describe exploitation through a specially crafted file provided to a user. CISA KEV status is false in the bundle, and no cited source here confirms active exploitation in the wild.
Researcher notes
Evidence supports arbitrary command execution via unsafe deserialization in a specific plugin function. The bundle does not provide exploit maturity, fixed version details, or compensating controls beyond vendor references, so validation should stay source-grounded.
Mitigation direction
- Inventory CODESYS Development System installations and identify versions 3.5.16 and 3.5.17.
- Check CODESYS vendor guidance for fixed versions or supported upgrade paths.
- Restrict users from opening untrusted CODESYS files from email, web downloads, or external partners.
- Prioritize EDR and application control on engineering workstations until upgrades are complete.
Validation and detection
- Confirm installed CODESYS Development System versions on engineering workstations.
- Review whether affected workstations receive project files from external or untrusted sources.
- Check endpoint telemetry for unexpected process execution originating from CODESYS tooling.
- Verify remediation status against the CODESYS advisory, not only package inventory labels.
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-2021-21868 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-2021-1305CVE 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.