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The GHOST bug is a buffer overflow security vulnerability in some distributions of Linux that can potentially enable attackers to execute arbitrary code on systems.

Specifically categorized as GHOST (gethostbyname) CVE-2015-0235, the GHOST bug flaw resides in the gethostbyname() and gethostbyname2() function calls in older versions of the GNU C Library (glibc) that is packaged with a variety of Linux distributions, including versions 5, 6 and 7 of Centos / RHEL / Fedora as well as Ubuntu 12.04.

In addition to older Linux distributions being vulnerable, applications and websites running on server hosts that use these older distributions may be susceptible to the GHOST bug as well, including Wordpress Web sites and various PHP applications.

Discovery of the GHOST Bug and Patches for the Vulnerability

The GHOST bug was first found and documented by security firm Qualys in early 2015. The GHOST vulnerability only affects older versions of the glibc library, as it was patched in the glibc-2.18 update, which debuted in August 2013.

However, while updated versions of glibc library have been available since 2013, it’s very common for enterprise servers to continue running older versions of Linux that are considered more stable. As a result, the GHOST bug has remained an open vulnerability for many enterprises despite patched versions of the glibc library being available.

While there isn't much evidence at this time of the GHOST bug being maliciously targeted by attackers, security researchers do recommend updating vulnerable installations of Linux as quickly as possible to prevent potential exploitation.

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