GHOST: glibc gethostbyname buffer overflow
During a code audit performed internally at Qualys, we discovered a buffer overflow in the __nss_hostname_digits_dots() function of the GNU C Library (glibc). This bug is reachable both locally and remotely via the gethostbyname*() functions, so we decided to analyze it -- and its impact -- thoroughly, and named this vulnerability "GHOST".
Solution is running command in your server's ssh:
RED HAT , CentOS , Clodulinux
yum -y update glibc
Debian , Ubuntu
apt-get upgrade glibc
Remember that after all restart your all services like FTP, http, exim, mysql, EXIm.