Skype v5.3.x - Transfer Buffer Overflow Vulnerability x64

Document Title:
===============
Skype v5.3.x - Transfer Buffer Overflow Vulnerability x64


References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=183


Release Date:
=============
2011-10-15


Vulnerability Laboratory ID (VL-ID):
====================================
183


Product & Service Introduction:
===============================
Skype ist eine kostenlose VoIP-Software mit Instant-Messaging-Funktion, Dateiübertragung und Videotelefonie, die 
ein proprietäres Protokoll verwendet. Sie ermöglicht das kostenlose Telefonieren zwischen Skype-Kunden via Internet 
sowie das gebührenpflichtige Telefonieren ins Festnetz und zu Mobiltelefonen (SkypeOut). Internettelefonate mit 
Kunden anderer Anbieter sind nicht möglich. Der ebenfalls gebührenpflichtige Dienst SkypeIn ermöglicht es, auch 
Anrufe aus dem herkömmlichen Telefonnetz entgegenzunehmen; solche Online-Nummern lassen sich für 25 Länder kaufen, 
ohne zwar physisch in diesen Ländern anwesend zu sein, jedoch rechtlich meist notwendigerweise einen Wohnsitz dort 
zu haben (bspw. Deutschland). In der aktuellen Version für Windows und Mac sind Konferenzschaltungen mit bis zu 25 
Gesprächsteilnehmern möglich.

(Copy of the Vendor Homepage: http://de.wikipedia.org/wiki/Skype)


Abstract Advisory Information:
==============================
Vulnerability-Lab team discovered a stable remote Buffer Overflow Vulnerability on Skypes Software v5.3.x  for windows 7.


Vulnerability Disclosure Timeline:
==================================
2011-06-08:	Vendor Notification
2011-06-09:	Vendor Response/Feedback
2011-09-17:	Vendor reproduce not successful!
2011-10-16:	Public or Non-Public Disclosure


Discovery Status:
=================
Published


Affected Product(s):
====================
Microsoft Corp.
Product: Skype - Software Client 5.5.0.113


Exploitation Technique:
=======================
Remote


Severity Level:
===============
High


Technical Details & Description:
================================
An buffer overflow vulnerability is detected on the windows version of skype. The Bug comes up when 
transfering files out of a unavailable stand-by mode on the system. The exploitation of the buffer overflow 
vulnerability allows an connected remote attacker to get privileges on the affected vulnerable system.


Vulnerable Module(s):
						[+] Data Transfer from unavailable Stand-by mode


Vulnerable OS:
						[+] Windows (x64)


Affected Version(s):
						Windows v5.3.0.120 & older versions

Picture(s):
						../1.png
						../2.png
						../3.png


Proof of Concept (PoC):
=======================
The vulnerability can be exploited by local & remote attackers with user inter -action. For demonstration or reproduce ...

Technique(s): 
=> Install 
=> Login 
=> Startup Data Transfer with user
=> Switch to Unavailable Mode 
=> Stand-by Mode 
=> Restart 
=> BEX - Buffer Overflow



Manually reproduce ...

1.  Install Skype Software
2.  Register an Account
3.  Login to your Skype
4.  Startup a transfer to your partner with any file
5.  Switch to Unavailable Mode on Skype
6.  Start your debugger on skype to catch the exception
7.  Go to the Stand-by mode of windows
8.  Restart from stand-by and login to your system
9.  Multiple unhandled BEX (buffer overflow) & APPCrash exceptions got droped by skype & the software crashs
10. Check debugger & enjoy the bof ...




--- Exception Logs ---
  Problemsignatur:
  Problemereignisname:	BEX
  Anwendungsname:	Skype.exe
  Anwendungsversion:	5.1.0.112
  Anwendungszeitstempel:4d4037c2
  Fehlermodulname:	StackHash_e98d
  Fehlermodulversion:	0.0.0.0
  Fehlermodulzeitstempel:00000000
  Ausnahmeoffset:	00000000
  Ausnahmecode:		c0000005
  Ausnahmedaten:	00000008
  Betriebsystemversion:	6.1.7600.2.0.0.768.3
  Gebietsschema-ID:	1031
  Zusatzinformation 1:	e98d
  Zusatzinformation 2:	e98dfca8bcf81bc1740adb135579ad53
  Zusatzinformation 3:	6eab
  Zusatzinformation 4:	6eabdd9e0dc94904be3b39a1c0583635


--- Report Logs ---
Version=1
EventType=BEX
EventTime=129435565109889129
ReportType=2
Consent=1
ReportIdentifier=2d471dfd-44e9-11e0-bd06-88112c285467
IntegratorReportIdentifier=2d471dfc-44e9-11e0-bd06-88112c285467
WOW64=1
Response.type=4
Sig[0].Name=Anwendungsname
Sig[0].Value=Skype.exe
Sig[1].Name=Anwendungsversion
Sig[1].Value=5.1.0.112
Sig[2].Name=Anwendungszeitstempel
Sig[2].Value=4d4037c2
Sig[3].Name=Fehlermodulname
Sig[3].Value=StackHash_e98d
Sig[4].Name=Fehlermodulversion
Sig[4].Value=0.0.0.0
Sig[5].Name=Fehlermodulzeitstempel
Sig[5].Value=00000000
Sig[6].Name=Ausnahmeoffset
Sig[6].Value=00000000
Sig[7].Name=Ausnahmecode
Sig[7].Value=c0000005
Sig[8].Name=Ausnahmedaten
Sig[8].Value=00000008
DynamicSig[1].Name=Betriebsystemversion
DynamicSig[1].Value=6.1.7600.2.0.0.768.3
DynamicSig[2].Name=Gebietsschema-ID
DynamicSig[2].Value=1031
DynamicSig[22].Name=Zusatzinformation 1
DynamicSig[22].Value=e98d
DynamicSig[23].Name=Zusatzinformation 2
DynamicSig[23].Value=e98dfca8bcf81bc1740adb135579ad53
DynamicSig[24].Name=Zusatzinformation 3
DynamicSig[24].Value=6eab
DynamicSig[25].Name=Zusatzinformation 4
DynamicSig[25].Value=6eabdd9e0dc94904be3b39a1c0583635
UI[2]=C:\\Program Files (x86)\\Skype\\Phone\\Skype.exe
UI[3]=Skype funktioniert nicht mehr
UI[4]=Windows kann online nach einer Lösung für das Problem suchen.
UI[5]=Online nach einer Lösung suchen und das Programm schließen
UI[6]=Später online nach einer Lösung suchen und das Programm schließen
UI[7]=Programm schließen
LoadedModule[0]=C:\\Program Files (x86)\\Skype\\Phone\\Skype.exe
LoadedModule[1]=C:\\Windows\\SysWOW64\\ntdll.dll
...  ...   ...  ...
LoadedModule[152]=C:\\Windows\\SysWOW64\\DCIMAN32.dll
LoadedModule[153]=C:\\Windows\\SysWOW64\\Dxtmsft.dll
LoadedModule[154]=C:\\Windows\\system32\\D3DIM700.DLL
LoadedModule[155]=C:\\Windows\\system32\\RICHED20.DLL
FriendlyEventName=Nicht mehr funktionsfähig
ConsentKey=BEX
AppName=Skype
AppPath=C:\\Program Files (x86)\\Skype\\Phone\\Skype.exe




Analyse(s):
		../AppCrash_Skype.exe_4a492d693dcf1f3150dab2f35a8de59b6675a845_114a483f
		../AppCrash_Skype.exe_627b3b712c7d99642dd448ada8f523c35904985_10327fba
		../AppCrash_Skype.exe_b3bfe07146a37ad586c5d73ed28f6055d48e7d_14a9921f


Security Risk:
==============
The security risk of the remote buffer overflow vulnerability is estimated as high(-) because of the system specific art of exploitation.


Credits & Authors:
==================
Vulnerability Research Laboratory - Benjamin Kunz Mejri (Rem0ve)


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=========================
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