Microsoft has re-released Service Pack 1 for SharePoint 2013, after deactivating the download link earlier this month.
Microsoft does not appear to have issued an official notice about the new SP1 on their website, though Microsoft’s download page indicates that the service pack was re-published on April 17th.
The new April 17 version of SP1 contains previously unreleased fixes, as well as a specific fix for a missing search box issue, although the KB article oddly mentions nothing about resolving the cumulative update problem.
SP1 for SharePoint Server 2013 notably adds compatibility with Windows Server 2012 R2. However, Microsoft’s new KB article notes that getting that compatibility requires
“a new installation of the full product from media.”