Cisco IOS XE does not properly manage memory for TFTP UDP flows, which allows remote attackers to cause a denial of service (memory consumption) via TFTP (1) client or (2) server traffic, aka Bug IDs CSCuh09324 and CSCty42686.
http://www.securitytracker.com/id/1029424
http://tools.cisco.com/security/center/content/CiscoSecurityNotice/CVE-2013-6704