This is primarily a maintenance release with minor bugfixes and improvements, and one security relevant fix for the Windows Interactive Service. Windows installer includes updated OpenVPN GUI and OpenSSL. Installer I601 included tap-windows6 driver 9.22.1 which had one security fix and dropped Windows Vista support. However, in installer I602 we had to revert back to tap-windows 9.21.2 due to driver getting reject on freshly installed Windows 10 rev 1607 and later when Secure Boot was enabled. The failure was due to the new, more strict driver signing requirements. The 9.22.1 version of the driver is in the process of getting approved and signed by Microsoft and will be bundled in an upcoming Windows installer.
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 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. Our long-term plan is to migrate to using MSI installers instead.
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.
OpenVPN GUI bundled with the Windows installer has a large number of new features compared to the one bundled with OpenVPN 2.3. One of major features is the ability to run OpenVPN GUI without administrator privileges. For full details, see the changelog. The new OpenVPN GUI features are documented here.
Please note that OpenVPN 2.4 installers will not work on Windows XP.
If you find a bug in this release, please file a bug report to our Trac bug tracker. In uncertain cases please contact our developers first, either using the openvpn-devel mailinglist or the developer IRC channel (#openvpn-devel at irc.freenode.net). For generic help take a look at our official documentation, wiki, forums, openvpn-users mailing list and user IRC channel (#openvpn at irc.freenode.net).