The krb5-appl packages provide Kerberos-aware telnet, ftp, rcp, rsh, andrlogin clients and servers. Kerberos is a network authentication systemwhich allows clients and servers to authenticate to each other usingsymmetric 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 coulduse this flaw to execute arbitrary code as root. (CVE-2011-4862) Note that the krb5 telnet daemon is not enabled by default in any versionof Red Hat Enterprise Linux. In addition, the default firewall rules blockremote access to the telnet port. This flaw does not affect the telnetdaemon distributed in the telnet-server package.For users who have installed the krb5-appl-servers package, have enabledthe krb5 telnet daemon, and have it accessible remotely, this update shouldbe applied immediately. All krb5-appl-server users should upgrade to these updated packages, whichcontain a backported patch to correct this issue.