Red Hat Security Advisory 2012-0306-03 - 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. It was found that ftpd, a Kerberos-aware FTP server, did not properly drop privileges. On Red Hat Enterprise Linux 5, the ftpd daemon did not check for the potential failure of the effective group ID change system call. If the group ID change failed, a remote FTP user could use this flaw to gain unauthorized read or write access to files that are owned by the root group.