I noticed a blog post today from Rob Wilcox, an Enterprise Vault trusted advisor, regarding confusion and difficulty that he was experiencing with determining if any cumulative hotfixes are installed on an EV server and, if so, exactly what ones are installed - https://www-secure.symantec.com/connect/blogs/enterprise-vault-version-numbers
This information is in fact readily available, if you know where to look, so I thought I'd pen this quick response for the benefit of Rob and anyone else experiencing the same problem.
The initial place to look for version related information on an Enterprise Vault server is in the registry (as explained in technote http://www.symantec.com/docs/TECH70211) at the following location - HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\KVS\Enterprise Vault\Install. Here you can see the main 'Version' installed and any CHF info in the relevant subkeys
In an Enterprise Vault version number, the first component represents the major release, the third component represents the service pack release, and the fourth component represents the specific build. For example:
10.0.4.1189 represents Enterprise Vault 10, Service Pack 4, Build 1189
Additionally for further information on CHFs installed, you can look at the file ...\Enterprise Vault\Installed Hotfixes\x.x.x.\AppliedHotfixes.txt to get a complete history of when cumulative hotfixes were installed and possibly uninstalled for that particular x.x.x release on that server
And if you really want to get deep into it, you can then drill down to the file ...\Enterprise Vault\Installed Hotfixes\x.x.x\x.x.x.x\Hotfix Info.txt to get precise details on the CHF, when it was installed, who installed it and exactly what files were changed by the install
So, in summary, we hope that we have made everything you can possibly want to know about a Cumulative Hotfix install available on an EV server, and the above will help you find what you need to know.