Hi,
EoL already announced for this part number and it is end of software maintenance by Aug 2018 which means there will be no bug fix provided in this version for any issues after this date.
https://www.cisco.com/c/en/us/products/collateral/unified-communications/unified-communications-manager-callmanager/eos-eol-notice-c51-738520.pdf
It is recommended to migrate to 11.5 (CM11.5-K9-NFR) before that time. I guess you will able to order this upgrade free of cost if you have a valid UCSS contract.
HTH
Rajan
Pls rate all useful posts