Canna is a Japanese input system available as free software. Canna provides a unified user interface for inputting Japanese. Canna supports Nemacs(Mule), kinput2 and canuum. All of these tools can be used by a single customization file, romaji-to-kana conversion rules and conversion dictionaries, and input Japanese in the same way. Canna converts kana to kanji based on a client-server model and supports automatic kana-to-kanji conversion. The Canna subsystem on certain UNIX versions contains a buffer overflow in the 'canuum' program. Canuum is a Japanese input tty frontend for Canna using uum. Certain versions have a buffer overflow via unchecked user supplied data in the -k,-c,-n options. Since this program is installed SUID root this attack will result in a root level compromise.