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).
A buffer overflow flaw was found in the MIT krb5 telnet daemon (telnetd). A remote attacker who can access the telnet port of a target machine could use this flaw to execute arbitrary code as root. (CVE-2011-4862)
Note that the krb5 telnet daemon is not enabled by default in any version of Red Hat Enterprise Linux. In addition, the default firewall rules block remote access to the telnet port. This flaw does not affect the telnet daemon distributed in the telnet-server package.
For users who have installed the krb5-workstation package, have enabled the telnet daemon, and have it accessible remotely, this update should be applied immediately.
All krb5-workstation users should upgrade to these updated packages, which contain a backported patch to correct this issue.