check-security-errata.sh

#!/bin/bash
# Downtimes are third Sunday of the month. In order to plan
# for upgrades and reboots, we email ourselves the list of all
# outstanding security updates for each system on the 2nd
# Wednesday of the month.
# Critical security update alerts are sent daily.
# Requires yum-plugin-security and mailx.

WEEKOFMONTH=$((($(date +%d)-1)/7+1))
DAYOFWEEK=$(date +%u)

if [ "$WEEKOFMONTH" = "2" -a "$DAYOFWEEK" = "3" ]; then
        SUMMARY=`/usr/bin/yum -q --security updateinfo`
        ERRATA=`/usr/bin/yum -q updateinfo list security 2>&1`
        SUBJECT="Security updates available for $HOSTNAME"
else
        SUMMARY="Critical errata advisory list:"
        ERRATA=`/usr/bin/yum -q updateinfo list security 2>&1 | grep -i 'Critical/Sec'`
        SUBJECT="CRITICAL Security updates available for $HOSTNAME"
fi

if [ ! -z "$ERRATA" ]; then
        echo -e "${SUMMARY}\n\n${ERRATA}" | mail -s "$SUBJECT" root
fi

This can be dropped in as-is into /etc/cron.daily. Just make sure the dependencies on yum-plugin-security and mailx are satisfied and that the file is chmod 0755.