Many people ask me we have different Linux version in one box.
[root@server1 ~]# cat /etc/redhat-release
CentOS release 6.5 (Final)
[root@server1 ~]# cat /etc/issue
CentOS release 6.4 (Final)
Kernel \r on an \m
Both above commands makes you confuse, you can simply get the correct version of linux by this command.
[root@server1 ~]# lsb_release -a
LSB Version: :base-4.0-amd64:base-4.0-noarch:core-4.0-amd64:core-4.0-noarch
Distributor ID: CentOS
Description: CentOS release 6.6 (Final)
Root Cause : Improper patching of servers.