Server 2012R2 Update failure - missing KB

Question

Hi,

I have a Windows Server 2012R2 vm (VMware) that has been refusing to install any updates since March this year and, after a lot of troubleshooting and various efforts to resolve (DISM/SFC, manual install, repair from media etc), I believe I've managed to pinpoint the problem down to a missing KB as per this in the CBS log:

2022-08-10 08:48:50, Info CBS Read out cached applicability from TiLight for package: Package_for_KB4338613~31bf3856ad364e35~amd64~~6.3.1.1, ApplicableState: 64, CurrentState:0
2022-08-10 08:48:51, Info CBS Session: 30977165_2713446094 initialized by client WindowsUpdateAgent.
2022-08-10 08:48:51, Info CBS Failed to internally open package. [HRESULT = 0x800f0805 - CBS_E_INVALID_PACKAGE]
2022-08-10 08:48:51, Info CBS Failed to OpenPackage using worker session [HRESULT = 0x800f0805]

KB4338613 isn't installed on any of the few 2012R2 servers we still have running and it doesn't appear to be available from MS anymore as it was superceded by future .NET security updates (some of which are installed. If there's no way of getting hold of the update, how do i go about patching this particular server if it constantly fails because of this elusive folder missing from WinSXS?