CVE-2021-21865: Codesys Development System

High severity, CVSS 7.8. EPSS: 1.3% chance of exploitation in the next 30 days.

A unsafe deserialization vulnerability exists in the PackageManagement.plugin ExtensionMethods.Clone() functionality of CODESYS GmbH CODESYS Development System 3.5.16. A specially crafted file can lead to arbitrary command execution. An attacker can provide a malicious file to trigger this vulnerability.

Affected products

• Codesys Development System: version 3.5.16.0 only; version 3.5.17.0 only

Published 2021-08-02. Last modified 2026-06-17.