OpenVPN versions before 2.3.3 and 2.4.x before 2.4.4 are vulnerable to a buffer overflow vulnerability when key-method 1 is used, possibly resulting in code execution.
https://lists.debian.org/debian-lts-announce/2022/05/msg00002.html
https://community.openvpn.net/openvpn/wiki/CVE-2017-12166