Security readout for executives and security teams
Plain-English summary
CVE-2021-21867 affects CODESYS Development System versions 3.5.16 and 3.5.17. A malicious file can trigger unsafe deserialization and allow arbitrary command execution. The business risk is compromise of an engineering workstation if a user opens or processes a crafted file.
Executive priority
Prioritize this for environments using CODESYS engineering tooling. The issue can compromise workstations used to manage industrial systems, but exploitation requires user interaction with a crafted file.
Technical view
The vulnerability is CWE-502 unsafe deserialization in ObjectManager.plugin ObjectStream.ProfileByteArray. The CVSS 3.0 score is 8.8, with network attack vector and required user interaction. Successful exploitation can affect confidentiality, integrity, and availability on the impacted system.
Likely exposure
Organizations are exposed where CODESYS Development System 3.5.16 or 3.5.17 is installed, especially engineering teams that receive project or configuration files from external parties.
Exploitation context
The provided sources describe malicious-file exploitation leading to arbitrary command execution. The bundle does not show CISA KEV listing or cited evidence of active exploitation in the wild.
Researcher notes
Evidence is sufficient for affected versions, vulnerability class, impact, and CVSS. The bundle does not provide exploit-in-the-wild evidence or a specific fixed version, so remediation should be tied to CODESYS advisory guidance.
Mitigation direction
- Identify installations of CODESYS Development System 3.5.16 and 3.5.17.
- Check CODESYS vendor guidance and apply the recommended update or workaround.
- Restrict opening CODESYS files to trusted sources and verified workflows.
- Isolate engineering workstations from unnecessary internet and email exposure.
- Ensure endpoint monitoring covers CODESYS-related process execution.
Validation and detection
- Confirm installed CODESYS Development System versions on engineering workstations.
- Review whether users handle externally supplied CODESYS project or profile files.
- Check security telemetry for suspicious child processes launched by CODESYS components.
- Verify vendor-recommended remediation 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-2021-21867 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-2021-1304CVE reference · x_refsource_MISC
- 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.