For more information do take a look at GHOST: glibc vulnerability (CVE-2015-0235)
GHOST is a 'buffer overflow' bug affecting the gethostbyname() and gethostbyname2() function calls in the glibc library. This vulnerability allows a remote attacker that is able to make an application call to either of these functions to execute arbitrary code with the permissions of the user running the application.
The gethostbyname() function calls are used for DNS resolving, which is a very common event. To exploit this vulnerability, an attacker must trigger a buffer overflow by supplying an invalid hostname argument to an application that performs a DNS resolution.
Update the glibc and ncsd packages on your system
Restart vulnerable services that use glibc (since so many services use glibc, the safest option is to restart the system).