This indicates an attack attempt to exploit a Denial of Service Vulnerability in atftp atftpd.
A remote attacker can exploit this vulnerability by sending a malformed TFTP ERROR packet to the target server. Successful exploitation could result in denial-of-service conditions.
atftp atftpd 0.7.1
Denial of Service: Remote attackers can crash vulnerable systems.
Refer to the Debian advisory for updates.