The operating system must be a supported release.
An operating system release is considered supported if the vendor continues to provide security patches for the product. With an unsupported release, it will not be possible to resolve security issues discovered in the system software.
Release Released Premier Support Extended Support
11 09 Nov 2011 NA NA
11.1 03 Oct 2012 NA NA
11.2 29 Apr 2014 NA NA
11.3 26 Oct 2015 01 Jan 2021 01 Jan 2027
11.4 28 Aug 2018 01 Nov 2031 01 Nov 2037
How this relates to the STIG checklist: STIG vs SCAP benchmark.