Re: IRM 004: ActiveSync Version 3.5 Denial of Service Vulnerability

From: panicat_private
Date: Tue Apr 01 2003 - 07:25:07 PST

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    In-Reply-To: <1048263395.5125.3.camel@Cadmium>
    
    I tried the sample DoS code, and it seems to do more than a DoS.
    I was able to crash applications beyond ActiveSync.
    This seems to me to indicate a write-overflow that *may* be exploitable
    to execute arbitrary code remotely.
    
    My system: Windows 2000, ActiveSync 3.1 (Build 9386)
    
    I have executed iPAQ_Crash 4 times, and each time I not only hung
    ActiveSync, but 3 out of 4 times I crashed another running application.
    
    1st time:
      Running ReflectionX 8.0.5 with two xterms open.
      Started ActiveSync.
      Ran iPAQ_Crash.
      Result:
        1. ActiveSync crashed.  It remained "green and spinning" like it
           was trying to load data.
        2. After a few seconds, "rx.exe" crashed (that's ReflectionX).
        3. ActiveSync remailed hung until I killed WCESCOMM.EXE (ActiveSync).
    
    2nd time:
      Restarted ReflectionX.
      Started ActiveSync.
      Ran iPAQ_Crash.
      Just ActiveSync hung.  Nothing else died.
    
    3rd time:
      Started Photoshop and Paint.
      Started ActiveSync.
      Started ReflectionX.
      Ran iPAQ_Crash.
      Photoshop crashed along with ActiveSync.
    
    4th time:
      Close Paint.
      Left ReflectionX running.
      Started Photoshop and minesweeper (games).
      Started ActiveSync.
      Ran iPAQ_Crash.
      Minesweeper crashed along with ActiveSync.
    
    "Which" applications crashes is unknown, but the more things running,
    the more likely something else will crash.  I suspect this has to
    do with a memory overflow.
    
    Knowing this, the overflow *may* be able to execute arbitrary code.
    (Unfortunately, I don't have a Windows debugger for validating this.)
    The original posting was for ActiveSync 3.5.  I was using ActiveSync 3.1.
    Perhaps the write-overflow only happens with 3.1?
    
    Can someone else verify this?
    
         -Neal
    
    
    >ActiveSync version 3.5 Denial of Service Vulnerability
    [snip]
    
    >Description:
    >~~~~~~~~~~~~
    >
    >By "pretending" to be an iPAQ and connecting to TCP port 5679, then 
    sending=
    > a corrupted "I would like to sync with you" packet, a NULL pointer is 
    dere=
    >ferenced in a call to the function WideCharToMultiByte() while it is 
    trying=
    > to process an entry within the packet. This then causes an application 
    err=
    >or, killing the "wcescomm" process.
    [snip]
    



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