Cisco ONS 15327 before 4.1(3), ONS 15454 before 4.6(1), ONS 15454 SD before 4.1(3), and Cisco ONS 15600 before 1.3(0) enable TFTP service on UDP port 69 by default, which allows remote attackers to GET or PUT ONS system files on the current active TCC in the /flash0 or /flash1 directories.