The issue stems from a heap-based buffer overflow found in the __nss_hostname_digits_dots() function in glibc. That particular function is used by the _gethostbyname function calls.
“A remote attacker able to make an application call either of these functions could use this flaw to execute arbitrary code with the permissions of the user running the application,” said an advisory from Linux distributor Red Hat.
The vulnerability, CVE-2015-0235, has already been nicknamed GHOST because of its relation to the _gethostbyname function. Researchers at Qualys discovered the flaw, and say it goes back to glibc version 2.2 in Linux systems published in November 2000.
According to Qualys, there is a mitigation for this issue that was published May 21, 2013 between patch glibc-2.17 versions and glibc-2.18. The patch, however, was not labeled a security fix at the time.