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Skype VoIP 5.2.x / 5.3.x Memory Corruption

Skype VoIP 5.2.x / 5.3.x Memory Corruption
Posted Aug 23, 2011
Authored by Benjamin Kunz Mejri | Site vulnerability-lab.com

A critical pointer vulnerability is located in the Mac OS X and Windows versions of Skype. The bug is located in 2 input forms of a unicode HTTP search request to the Skype search directory server. The vulnerability allows a local attacker to crash the complete Skype process via an unknown unhandled software exception. The bug allows a local attacker to overwrite or read a new address (skype_debug2_win7_x64x.png).

tags | advisory, web, local
systems | windows, apple, osx
SHA-256 | ecad962852550d791ca6abfe3c2523e48124d32e8c4270d0824d797e4340408b

Skype VoIP 5.2.x / 5.3.x Memory Corruption

Change Mirror Download
Skype VoIP v5.2.x & v5.3.x - Critical Pointer Vulnerability




Skype is a famous software application that allows users to make voice and video calls and chats
over the Internet. Calls to other users within the Skype service are free, while calls to both traditional
landline telephones and mobile phones can be made for a fee using a debit-based user account system.
Skype has also become popular for its additional features which include instant messaging, file transfer,
and videoconferencing. Skype has 663 million registered users as of 2010. The network is operated by
Skype Limited, which has its headquarters in Luxembourg.
In 2011 Microsoft bought the skype company & the software is now a official microsoft product.

(Copy of the website: http://en.wikipedia.org/wiki/Skype)

Vulnerability-Lab team discovered a critical Pointer Vulnerability on the Skype VoIP v5.2.x & v5.3.x Software.

2011-07-02: Vendor Notification
2011-07-04: Vendor Response/Feedback
2011-07-24: Vendor Fix/Patch
2011-08-22: Public or Non-Public Disclosure


Affected Products:



A critical pointer vulnerability is located in the macosx & windows version of skype. The bug/vulnerability is located in
2 input forms of an uni-code http search request to the skype search directory server. The vulnerability allows an local attacker
to crash the complete skype process via an unknown unhandled software exception(memory-corruption). The bug allows an local
attacker also to overwrite or read a new adress(skype_debug2_win7_x64x.png).

Vulnerable Module(s):
[+] Input Mask - Geschäftsempfehlungen finden - Wo? & Was?

[+] MacOS v5.2.0.1523
[+] Windows (x32&x64) - v5.3.0.120

--- Violation Exception Log ---
0:034> g
(f10.ed4): Unknown exception (first chance)
(f10.ed4): Access violation - code c0000005 (first chance)
First chance exceptions are reported before any exception handling.
This exception may be expected and handled.
eax=c07ca54b ebx=a96959bc ecx=d8f10db2 edx=0000155f esi=d7263481 edi=3e294540
eip=25c50116 esp=37f91000 ebp=50601616 iopl=0 nv up ei pl nz na po nc
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010202
25c50116 cd01 int 1
0:000> !exchain
Skype+8be3a0 (00cbe3a0)

--- MacOS Exception Logs ---
Process: Skype [61937]
Path: /Applications/Skype.app/Contents/MacOS/
Identifier: com.skype.skype

Version: (
Code Type: X86 (Native)
Process: launchd [166]

Date/Time: 2010-10-04 21:35:07.689 +0200
Version: Mac OS X 10.6.4 (10F569)
Report Version: 6
Interval Since Last Report: 2972640 sec
Crashes Since Last Report: 1118
Per-App Interval Since Last Report: 2630974 sec
Per-App Crashes Since Last Report: 3

Anonymous UUID: 2DCE5869-9F5B-46AD-950A-2295F0CBFC3A
Exception Codes: 0x0000000000000000, 0x0000000000000000
Crashed Thread: 6

[+] exception_log_osx.txt

--- Windows Exception Logs ---
0:000> .exr 0xffffffffffffffff
ExceptionAddress: 25c50116
ExceptionCode: c0000005 (Access violation)
ExceptionFlags: 00000000
NumberParameters: 2
Parameter[0]: 00000000
Parameter[1]: ffffffff
Attempt to read from address ffffffff
0:000> lmvm Skype
start end module name
00400000 01d50000 Skype (no symbols)
Loaded symbol image file: C: Program Files (x86) \\Skype\\ Phone\\ Skype.exe
Image path: C: Program Files (x86)\\ \\Skype\\ \\Phone\\ Skype.exe
Image name: Skype.exe
Timestamp: Thu May 13 15:11:32 2010 (4BEBFA84)
CheckSum: 01908D73
ImageSize: 01950000
File version:
Product version:
File flags: 8 (Mask 3F) Private
File OS: 4 Unknown Win32
File type: 1.0 App
File date: 00000000.00000000
Translations: 0409.04e4
CompanyName: Skype Technologies S.A.
ProductName: Skype
InternalName: Skype.exe
OriginalFilename: Skype.exe
ProductVersion: 4.2
FileDescription: Skype
LegalCopyright: (c) Skype Technologies S.A.


2011-07-24: Vendor Fix/Patch - Skype decided to exclude the skype user directory 2011-06/2011.07

The security risk of the local exploitable memory corruption vulnerability is estimated as high.

Vulnerability Research Laboratory - Benjamin Kunz Mejri (Rem0ve)

The information provided in this advisory is provided as it is without any warranty. Vulnerability-Lab disclaims all warranties,
either expressed or implied, including the warranties of merchantability and capability for a particular purpose. Vulnerability-
Lab or its suppliers are not liable in any case of damage, including direct, indirect, incidental, consequential loss of business
profits or special damages, even if Vulnerability-Lab or its suppliers have been advised of the possibility of such damages. Some
states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation
may not apply. Any modified copy or reproduction, including partially usages, of this file requires authorization from Vulnerability-
Lab. Permission to electronically redistribute this alert in its unmodified form is granted. All other rights, including the use of
other media, are reserved by Vulnerability-Lab or its suppliers.

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