Wednesday, August 11, 2010

MS SMB Remote Trans2 Zero Size Pool Allocation (MS10-054)

This SMBv1 vulnerability has been disclosed to MS back in february 2010 and patched this month in MS10-054 bulletin.

This vulnerability is quite interesting since it's present in all Windows version since Windows 2000, and can be triggered easily in at least 2 different Trans2 opcode by setting a Max Data Count to 0;
- QUERY_FS_INFO Query FS Attribute Info
- QUERY_FS_INFO, Query FS Volume Info

You can find the full advisory here:
SRD blog entry:

Wednesday, May 12, 2010

Fuzzing lib released

This is a fuzzing lib I've been working on for a while (it's not a complete one, but still pretty powerfull), you can adapt it very easily to your fuzzer by invoking ;

import lib
from lib import *

Then you call one specific function, or randfunc().
randfunc will basicaly choose randomly the function in the lib to fuzz with. 

Here's a quick example using this lib;   -- > this is not a smb fuzzer, it's simply an example of using this lib....

And yes you need to include the lib, which is located here ;

Enjoy !

Saturday, April 17, 2010


This bug was discovered back in december 2009, and patched by microsoft in April 2010.
This issue is a basic stack overflow affecting only windows 7/2008R2 smb1 implementation.
It's actually a nice bug as the affected function is not protected by a canary, and allow us to redirect the flow anywhere we want to.
You can find the full advisory about this bug here :
Have phun !
PoC url :

Thursday, April 15, 2010

Turning SMB client bug to server side

This blog post is about a technic to automate with no user interaction at all SMB client side bug exploitation targeting the Domain Master Browser (DMB) or PDC  (only the PDC can be a DMB)which is basicaly the perfect target in a pentest. Targeting the DMB is perfect, simply because if you control that box, you'll control all computer joined to this box tree.

Since the SRD is once again downplaying SMB client side bug i think it's important to share this kind of tricks.

It's also important to mention that Browser and NBNS abusing is well known since a long time, as theses protocols wasn't developed with security in mind, this blog post is a simple real case example.

There's two way to automate SMB client side bug;
  • NBNS Spoofing (require some "kind" of user interaction in some way,   anyways  in a corporate network it works pretty well)
  • Browser Protocol Abusing (the funny one)
In this case I will cover a form of Browser Protocol Abusing.

The basic goal of this attack is to hijack the Local Master Browser (LMB), and there's various way to do so;
  • Register via NBNS on the Workgroup or domain, and launch an election (zero filled election packet), the winning criteria is first the browser version, and then the box capabilities, which is controlled by us.
  • Create a NBNS name/ip conflict with the LMB and after 3 shot send a "Name Overwrite Demand" packet
  • Reset the LMB 
Why targeting the LMB ?
Simple, the Backup browser will sync via SMB (NetServerEnum2) on the LMB every 15 mn.
We don't care that much about the Backup Browser, what we want it's the DMB, and guess what, he's also syncing on the LMB as soon you send him a Browser MasterAnnouncement :]

In this case, i will wait for a HostAnnouncement, a  LocalMasterAnnouncement or an ElectionResquest, then I will send two LMB ResetBrowserState;
- one Reset_state clear_all
- one Reset_state stop_master

Which will directly kill the LMB (at least on Windows implementation).
Then you can launch an election that you're sure to win (as mentionned before),
make a Local Master Browser Announcement, and finally a MasterAnnouncement, then the DMB will connect direclty to your fake server and get pwned (or not).

Here's a quickly made proof of concept which work pretty well , it also have a NBNS spoofer just in case an admin try to access a share:]

I included a proof of concept for a previously discovered bug patched in february (MS10-006), you can find the full advisory here:

Note: Make sure your SMB server/exploit listen on 139 and 445, and can handle NBSS session request, if not, you wont get any candy.

Since Blogger is not python friendly:

A bug like MS10-006 can be easily wormable if exploited with this kind of approach.

Tuesday, February 9, 2010

More details on MS10-006

An Advisory as been released by Microsoft patching MS10-006.
This vulnerability as been found back in november while testing some client side vulnerability on SMB.
A full advisory regarding the details of this issue is located here

Regarding the SRD statement for smb client possible exploitation i'd like to add & post a small tool abusing netbios name service functionnality.
Ronald Bowes did some great work with nbtool for such purpose.

You can find a small version in python here;

Basicly, anyone on the segment using :
net use \\blabla\share
net view \\blabla\share
dir \\blabla\share
On vista/7/server2008|R2 it's also possible to use start -> search box --> \\existing_machine\share

Any of these command result in a NBNS query asking which IP is using this netbios name
Then this small utility will answer it's at "attacker_IP".
Once the ip resolved, the machine will initiate a smb connection to that IP.
You can also abuse the BROWSER service for same kind of purpose, I will post a full entry when i get some free time ...