Extended support
From Atomicorp Wiki
Centos
Centos 5
Support is not available for Centos 5 after March 31, 2017.
Redhat 5
Customers must also purchase an Extended Life-cycle Support (ELS) add-on subscription from Redhat to support the operating system and its components. RHEL5 systems without ELS add-on subscriptions from Redhat are not supported.
Customers may purchase annual an Extended Support Contract (ESC) to support Redhat 5 after March 31, 2017. Contact sales for details.