The MITRE CVE dictionary describes this issue as:
The vfprintf function in stdio-common/vfprintf.c in libc in GNU C Library (aka glibc) 2.12 and other versions does not properly calculate a buffer length, which allows context-dependent attackers to bypass the FORTIFY_SOURCE format-string protection mechanism and cause a denial of service (stack corruption and crash) via a format string that uses positional parameters and many format specifiers.
Find out more about CVE-2012-3404 from the
MITRE CVE dictionary dictionary and
This issue did not affect the version of glibc as shipped with Red Hat Enterprise Linux 5.