Security readout for executives and security teams
Plain-English summary
CVE-2021-21863 affects CODESYS Development System 3.5.16 and 3.5.17. Opening a maliciously crafted file can allow arbitrary command execution on the workstation. This is most urgent for engineering teams that exchange or import CODESYS files from external or less-trusted sources.
Executive priority
Treat as high priority for OT engineering environments because compromise of a development workstation can affect sensitive automation projects and downstream operational integrity. Prioritize inventory, vendor guidance, and controls around untrusted files.
Technical view
The issue is unsafe deserialization, CWE-502, in ComponentModel Profile.FromFile(). The CVSS 3.0 score is 8.8 with network attack vector, no privileges required, and user interaction required. Successful exploitation can compromise confidentiality, integrity, and availability on the affected system.
Likely exposure
Exposure is likely limited to systems running CODESYS Development System 3.5.16 or 3.5.17, especially engineering workstations that open project, profile, or related files received from others.
Exploitation context
The provided sources do not show CISA KEV listing or active exploitation. The attack depends on convincing a user to open or process a specially crafted file; no exploit steps are included in the public bundle.
Researcher notes
Evidence is limited to CVE metadata and the CODESYS reference URL. The bundle identifies the vulnerable function and affected versions, but does not provide a named fixed release, detailed advisory text, or confirmed exploitation evidence.
Mitigation direction
- Identify any CODESYS Development System 3.5.16 or 3.5.17 installations.
- Check CODESYS vendor guidance for fixed versions or official mitigations.
- Avoid opening untrusted CODESYS-related files on engineering workstations.
- Restrict file exchange paths to trusted sources and controlled repositories.
- Apply least-privilege controls to engineering workstation user accounts.
Validation and detection
- Query asset inventory for CODESYS Development System versions 3.5.16 and 3.5.17.
- Confirm which teams import external or supplier-provided CODESYS files.
- Review endpoint logs for unusual process launches from CODESYS workstations.
- Verify vendor advisory status before declaring remediation complete.
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-2021-21863 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
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.