Hello
Although the following issues have been reported, or RouterOS is affected by this problem?
http://www.kb.cert.org/vuls/byvendor?searchview&Query=FIELD+Reference=852879&SearchOrder=4
http://support.ntp.org/bin/view/Main/SecurityNotice
only partially, but next RouterOS version will have new and upgraded NTP
Fixed version has been released http://forum.mikrotik.com/t/v6-24-rc/83927/1