GHOST vulnerability in the GNU C library (glibc) is a serious vulnerability (CVE-2015-0235) that involves a heap-based buffer overflow in the glibc function name – “GetHOSTbyname()” PHP applications, including WordPress Content Management System (CMS) could also be affected by the bug. The vulnerability has been present in the code since 2000, but was not marked as a security vulnerability so the fix did not make it into common Linux distributions like RedHat and Ubuntu.
Source: https://thehackernews.com/2015/01/ghost-linux-security-vulnerability_29.html