Updated krb5 packages that fix a security issue are now available for Red Hat Enterprise Linux 2.1 and 3. This update has been rated as having critical security impact by the Red Hat Security Response Team.
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 (KDC). An input validation flaw was found in the ASN.1 (Abstract Syntax Notation One) decoder used by MIT Kerberos. A remote attacker could use this flaw to crash a network service using the MIT Kerberos library, such as kadmind or krb5kdc, by causing it to dereference or free an uninitialized pointer or, possibly, execute arbitrary code with the privileges of the user running the service. (CVE-2009-0846) All krb5 users should upgrade to these updated packages, which contain a backported patch to correct this issue. All running services using the MIT Kerberos libraries must be restarted for the update to take effect.