Kerberos is a networked authentication system which allows clients and servers to authenticate to each other with the help of a trusted third party, the Kerberos KDC. It was found that if a KDC served multiple realms, certain requests could cause the setup_server_realm function to dereference a NULL pointer. A remote, unauthenticated attacker could use this flaw to crash the KDC using a specially crafted request. A NULL pointer dereference flaw was found in the MIT Kerberos SPNEGO acceptor for continuation tokens. A remote, unauthenticated attacker could use this flaw to crash a GSSAPI-enabled server application. A buffer overflow was found in the KADM5 administration server when it was used with an LDAP back end for the KDC database. A remote, authenticated attacker could potentially use this flaw to execute arbitrary code on the system running kadmind. Two buffer over-read flaws were found in the way MIT Kerberos handled certain requests. A remote, unauthenticated attacker who is able to inject packets into a client or server application"s GSSAPI session could use either of these flaws to crash the application. A double-free flaw was found in the MIT Kerberos SPNEGO initiators. An attacker able to spoof packets to appear as though they are from an GSSAPI acceptor could use this flaw to crash a client application that uses MIT Kerberos. These updated krb5 packages also include several bug fixes. Space precludes documenting all of these changes in this advisory. Users are directed to the Red Hat Enterprise Linux 6.6 Technical Notes, linked to in the References section, for information on the most significant of these changes. All krb5 users are advised to upgrade to these updated packages, which contain backported patches to correct these issues.