kernel-3.18.25-20, with a fix for XSA-174, has been built in the cbs and is making its way through the system. It should be in centos-virt-xen-testing for both CentOS 6 and CentOS 7 shortly, and a signed version should be in mirrors after tomorrow's signing run.

(This should be suitable for either people using Xen 4.6 or Xen 4.4.)

Please test it and report any errors here.

Thanks, -George