OpenVPN before 2.6.11 does not santize PUSH_REPLY messages properly which attackers can use to inject unexpected arbitrary data into third-party executables or plug-ins.
https://www.cisa.gov/news-events/ics-advisories/icsa-24-319-06
https://tuxcare.com/blog/ubuntu-fixes-two-openvpn-vulnerabilities/
https://www.mail-archive.com/[email protected]/msg07634.html