Following  is  based  on  "Proof  of  Concept"  Security Advisory.
    NcFTPd is a commercial FTP (File Transfer Protocol) server, in the
    NcFTP product  line.   The source  code is  not publicly released.
    This was  tested on  Linux with  libc5 (there's  a glibc2 specific
    version available).   NcFTPd's PORT parsing  function has a  stack
    buffer overflow  problem, which  would basically  allow a  user to
    remotely execute arbitrary code - the thing here is that the  PORT
    parsing function seem  to change characters,  that are not  in the
    range 0x30-0x39  (ASCII '0'-'9'),  into 0x20  (ASCII space), hence
    making  an  exploit  almost  impossible  (note that, if ascii 0x40
    would be allowed  that would be  a different story).   The program
    only parses for characters out of the 0-9 range in a specific area
    in memory (the  one that contains  return address heh)  - the rest
    is kept  unchanged, and  you can't  really go  further in  memory,
    input line size is restricted.

    The current bug is not really a problem, it can crash the child
    process with a segfault, the parent process receives a signal 6
    (abort) and the child process stay zombie for a few seconds and a
    brand new one is created.  Example:

        evil:$ nc victim ftp
        220 victim NcFTPd Server (unregistered copy) ready.
        user anonymous
        331 Guest login ok, send your complete e-mail address as password.
        pass some@thing
        230-You are user #1 of 50 simultaneous users allowed.
        230 Logged in anonymously.
        port 00000000000000000000000000000000000000000000 (...)
        501 Syntax error in parameters.

    So, this can occur  if an attacker uses  64 or more characters  in
    the range of '0' to '9' in an FTP "PORT" command.  This can  cause
    the  child  process  handling  the  FTP  connection  to  crash and
    respawn, but does not leave an attacker with root privileges.  For
    reference, here is a snippet which illustrates the actual problem:

         static int
         ftp_aton(const char *cp, struct sockaddr_in *sinaddr)
                char buf[64];
                char *dst;
                char *dstlim;
                int i, c;
                unsigned int octets[6], u;

                memset(sinaddr, 0, sizeof(struct sockaddr_in));
                dst = buf;
        -       dstlim = dst + sizeof(buf);
        +       dstlim = dst + sizeof(buf) - 1;

                for ( ; ; ) {
                        c = (int) *cp++;
                        if (c == '\0')
                        if (! isdigit(c))
                                 c = ' ';
                        if (dst < dstlim)
                                 *dst++ = c;
                *dst = '\0';


    NcFTPd 2.4.1 is available which fixes this problem.