Security readout for executives and security teams
Plain-English summary
CVE-2021-21866 affects CODESYS Development System versions 3.5.16 and 3.5.17. A malicious file opened by a user can cause code execution on the engineering workstation. The business risk is highest where CODESYS is used to manage industrial control or automation projects.
Executive priority
Treat this as a high-priority engineering workstation risk, not a broad internet-facing server issue. Prioritize sites using affected CODESYS versions for operational technology work.
Technical view
The issue is unsafe deserialization in ObjectManager.plugin ProfileInformation.ProfileData, classified as CWE-502. The CVSS 3.0 score is 8.8 with network attack vector, low complexity, no privileges required, and required user interaction. Successful exploitation can affect confidentiality, integrity, and availability.
Likely exposure
Exposure is likely limited to environments running CODESYS Development System 3.5.16 or 3.5.17, especially engineering workstations that receive project or profile files from outside trusted channels.
Exploitation context
The supplied sources describe exploitation through a specially crafted file and required user interaction. The bundle does not indicate CISA KEV listing or active exploitation evidence.
Researcher notes
Evidence supports arbitrary command execution through unsafe deserialization when a malicious file is processed. The supplied bundle does not name a fixed version or confirm exploitation in the wild, so remediation should be tied to CODESYS advisory guidance.
Mitigation direction
- Inventory CODESYS Development System versions on engineering workstations.
- Review CODESYS vendor guidance for the affected 3.5.16 and 3.5.17 versions.
- Prevent users from opening untrusted CODESYS-related files.
- Isolate engineering workstations from general email and web browsing paths.
- Monitor endpoints for suspicious execution after opening project files.
Validation and detection
- Confirm whether CODESYS Development System 3.5.16 or 3.5.17 is installed.
- Identify workflows that import or open external CODESYS files.
- Check endpoint logs for unusual process launches from CODESYS directories.
- Verify vendor-recommended remediation has been applied where applicable.
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-2021-21866 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://talosintelligence.com/vulnerability_reports/TALOS-2021-1301CVE reference · x_refsource_MISC
- https://customers.codesys.com/index.php?eID=dumpFile&t=f&f=16805&token=ee583c498941d9fda86490bca98ff21928eec08a&download=CVE reference · x_refsource_CONFIRM
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.