Windows Server 2012 is supported from ESSO Version 8.06 onwards.
Note that Windows Server 2012 is 64-bit only.
The latest release of ESSO 8.0.6 can be downloaded here: Enterprise Single Sign-On - Download Software
Existing 8.05 clients can continue to work with an ESSO 8.0.6 sever, however, any new functionality (please refer to the 8.0.6 release notes for more information, Enterprise Single Sign-On - Technical Documentation
) will not be available to those clients.
Please note that the latest version of Enterprise Single Sign-On is 9.0 and is available here