Just asking if there is any known exploit that allows a client connected a win server 2003 sp2 x64 via SunRay thin-client to infiltrate (or preform a local privilege escalation on) the server. The thin clients currently have limited privileges, no cd/usb input and neither the server nor the clients have any internet access.
Windows Server 2003 SP2 is out of MSFT's support lifecycle. Microsoft requires your server to be at SP3 in order to be eligible for security and other hotfixes.
Your server is vulnerable all the security patches that SP3 fixed. Of course your deployment mitigates this somewhat.
If the SunRay thin client issues an RDP call to your server, and the ethernet cable to the thin client is disconnected and placed into a laptop (etc), then the RDP could be exploited. There are several known issues with unpatched RDP.
There are also MITM issues with Win2003 RDP if the attacker saw an administrator log in from another machine.