If you are managing or developing for this specific build, keep the following in mind:
Interestingly, the kernel file ( ntoskrnl.exe ) for build 6003 still reports its as 6.0.6003, not 6.1 (Windows 7) or 6.2 (Windows 8). The NT major version remains 6.0—Microsoft never changed the core NT version for Server 2008. windows server 2008 build 6003 upd
Without Build 6003, your Server 2008 is frozen at January 2020’s security level – over four years behind. If you are managing or developing for this
Build 6003 is the of Windows Server 2008. No new updates will change that number again. Build 6003 is the of Windows Server 2008
To understand Build 6003, one must look at the release timeline. The gold master (RTM) release of Windows Server 2008 was . Following the release to manufacturing, development continued on the Service Pack 2 (SP2) branch.
Microsoft never officially documented the change, but analysis of the update reveals:
During the ESU period, Microsoft continued releasing monthly security rollups. In (pre-ESU, as a preview), one specific update—KB4489887 (for Windows Server 2008 SP2)—unexpectedly incremented the kernel build number from 6002 to 6003 .