glibc contains a vulnerability that allows specially crafted LD_LIBRARY_PATH values to manipulate the heap/stack, causing them to alias, potentially resulting in arbitrary code execution. Please note that additional hardening changes have been made to glibc to prevent manipulation of stack and heap memory but these issues are not directly exploitable, as such they have not been given a CVE. This affects glibc 2.25 and earlier.
Fixed in glibc-2.12-1.209.el6_9.2.x86_64.rpm
The Unitrends security update dated 08/31/2017 or later includes this fix.