Updated krb5 packages that fix three security issues are now available for Red Hat Enterprise Linux 6. The Red Hat Security Response Team has rated this update as having important security impact. Common Vulnerability Scoring System base scores, which give detailed severity ratings, are available for each vulnerability from the CVE links in the References section. Description Kerberos is a network authentication system which allows clients and servers to authenticate to each other using symmetric encryption and a trusted third-party, the Key Distribution Center . A NULL pointer dereference flaw was found in the way the MIT Kerberos KDC processed principal names that were not null terminated, when the KDC was configured to use an LDAP back end. A remote attacker could use this flaw to crash the KDC via a specially-crafted request. A denial of service flaw was found in the way the MIT Kerberos KDC processed certain principal names when the KDC was configured to use an LDAP back end. A remote attacker could use this flaw to cause the KDC to hang via a specially-crafted request. A denial of service flaw was found in the way the MIT Kerberos V5 slave KDC update server processed certain update requests for KDC database propagation. A remote attacker could use this flaw to terminate the kpropd daemon via a specially-crafted update request. Red Hat would like to thank the MIT Kerberos Team for reporting the CVE-2011-0282 and CVE-2011-0281 issues. Upstream acknowledges Kevin Longfellow of Oracle Corporation as the original reporter of the CVE-2011-0281 issue. All krb5 users should upgrade to these updated packages, which contain backported patches to correct these issues. After installing the updated packages, the krb5kdc daemon will be restarted automatically.