(RHSA-2012:1097) Moderate: glibc security and bug fix update

The glibc packages provide the standard C and standard math libraries used
by multiple programs on the system. Without these libraries, the Linux
system cannot function properly.

It was discovered that the formatted printing functionality in glibc did
not properly restrict the use of alloca(). This could allow an attacker to
bypass FORTIFY_SOURCE protections and execute arbitrary code using a format
string flaw in an application, even though these protections are expected
to limit the impact of such flaws to an application abort. (CVE-2012-3406)

This update also fixes the following bug:

• If a file or a string was in the IBM-930 encoding, and contained the
  invalid multibyte character “0xffff”, attempting to use iconv() (or the
  iconv command) to convert that file or string to another encoding, such as
  UTF-8, resulted in a segmentation fault. With this update, the conversion
  code for the IBM-930 encoding recognizes this invalid character and calls
  an error handler, rather than causing a segmentation fault. (BZ#837896)

All users of glibc are advised to upgrade to these updated packages, which
contain backported patches to fix these issues.