(RHSA-2011:1852) Critical: krb5-appl security update

The krb5-appl packages provide Kerberos-aware telnet, ftp, rcp, rsh, and
rlogin clients and servers. 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-appl-servers package, have enabled the
krb5 telnet daemon, and have it accessible remotely, this update should be
applied immediately.

All krb5-appl-server users should upgrade to these updated packages, which
contain a backported patch to correct this issue.