This is primarily a maintenance release with bugfixes and improvements. One of the big things is enhanced TLS 1.3 support. A summary of the changes is available in Changes.rst, and a full list of changes is available here.
Please note that LibreSSL is not a supported crypto backend. We accept patches and we do test on OpenBSD 6.0 which comes with LibreSSL, but if newer versions of LibreSSL break API compatibility we do not take responsibility to fix that.
Also note that Windows installers have been built OPENVPN WINDOWS XP with NSIS version that has been patched against several NSIS installer code execution and privilege escalation problems. Based on our testing, though, older Windows versions such as Windows 7 might not benefit from these fixes. We thus strongly encourage you to always move NSIS installers to a non-user-writeable location before running them. We are moving to MSI installers in OpenVPN 2.5, but OpenVPN 2.4.x will remain NSIS-only.
Compared to OpenVPN 2.3 this is a major update with a large number of new features, improvements and fixes. Some of the major features are AEAD (GCM) cipher and Elliptic Curve DH key exchange support, improved IPv4/IPv6 dual stack support and more seamless connection migration when client’s IP address changes (Peer-ID). Also, the new —tls-crypt feature can be used to increase users’ connection privacy.