The MITRE CVE dictionary describes this issue as:
Integer overflow in the __vstrfmon_l function in stdlib/strfmon_l.c in the strfmon implementation in the GNU C Library (aka glibc or libc6) before 2.10.1 allows context-dependent attackers to cause a denial of service (application crash) via a crafted format string, as demonstrated by the %99999999999999999999n string, a related issue to CVE-2008-1391.
Find out more about CVE-2009-4881 from the
MITRE CVE dictionary dictionary and
Red Hat does not consider this bug to be a security issue. Properly written application should not use arbitrary untrusted data as part of the format string passed to functions as strfmon or printf family functions.