A vulnerability was discovered and corrected in rsyslog:

Stack-based buffer overflow in the parseLegacySyslogMsg function
in tools/syslogd.c in rsyslogd in rsyslog 4.6.x before 4.6.8 and
5.2.0 through 5.8.4 might allow remote attackers to cause a denial of
service (application exit) via a long TAG in a legacy syslog message
(CVE-2011-3200).

The updated packages have been patched to correct this issue.

Update:

rsyslog was upgraded to the 5.8.5 version for Mandriva Linux 2011
that brings additional fixes as well.