(RHSA-2011:1853) Critical: krb5 security update

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.