Kernel drivers in Beckhoff TwinCAT 3.1 Build 4022.4, TwinCAT 2.11 R3 2259, and TwinCAT 3.1 lack proper validation of user-supplied pointer values. An attacker who is able to execute code on the target may be able to exploit this vulnerability to obtain SYSTEM privileges.
https://srcincite.io/advisories/src-2018-0007/
https://ics-cert.us-cert.gov/advisories/ICSA-18-081-02
https://download.beckhoff.com/download/Document/product-security/Advisories/advisory-2018-001.pdf