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AUSCERT External Security Bulletin Redistribution
ESB-2008.0124 -- [Win]
Skypefind Cross Zone Scripting Vulnerability
6 February 2008
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AusCERT Security Bulletin Summary
---------------------------------
Product: 3.6.0.244 and prior
Publisher: Skype
Operating System: Windows
Impact: Execute Arbitrary Code/Commands
Access: Remote/Unauthenticated
CVE Names: CVE-2008-0582 CVE-2008-0583
Original Bulletin: http://skype.com/intl/en/security/skype-sb-2008-002.html
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SKYPE-SB/2008-002: Skypefind Cross Zone Scripting Vulnerability
Bulletin title: Skypefind Cross Zone Scripting Vulnerability
Bulletin ID: SKYPE-SB/2008-002
Bulletin status: FINAL
Date of announcement: 2008-01-31 11:00:00 +0000
Products affected: Skype for Windows
Vulnerability type: Cross Zone Scripting
CVE references:
Risk assessment: MEDIUM
CVSS base score: 7.8 (AV:N/AC:M/Au:Mu/C:C/I:C/A:C)
Cross-references:
http://www.skype.com/intl/en/security/skype-sb-2008-001-update1.html
http://aviv.raffon.net/2008/01/17/SkypeCrosszoneScriptingVulnerability.aspx
Table of contents:
1. Problem description and brief discussion
2. Impact and affected software
3. Solution or work-around
4. Special instructions and notes
5. Software download location
6. Authenticity verification
7. Common Vulnerability Scoring System (CVSS) assessment
8. Credits and additional information
9. Bulletin release history
10. Notices
1. Problem description and brief discussion
Description
Skype uses Internet Explorer web control to render HTML content for
different webapplications, including SkypeFind.
A vulnerability has been found in the Skypefind which allows attacker
to execute arbitrary code when victim is navigating to the SkypeFind
directory item (business contact) which submitted in special way.
There is one important precondition for the exploit to work: victim
must receive Skype contact request authorization from the attacker's
Skype account.
This vulnerability is exploitable because of security zone elevation
vulnerability in skype client (see Skype Security Bulletin
SKYPE-SB/2008-001 and links in Cross References section above) which
allows scripts to be run in Local Zone security context in IE web
control used to render SkypeFind content.
2. Impact and affected software
Impact
A user of Skype for Windows who either a) navigates directly to the
SkypeFind specially submitted business contact or b) when searching
for business contacts is presented with result page which includes
specially submitted business contact may experience execution of
arbitrary code without consent.
Affected software
3. Solution or work-around
Skype has fixed the vulnerability in Skypefind
4. Special instructions and notes
None.
5. Software download location
The preferred method for installing security updates is to download
the software directly from Skype's website, from the website of
Skype's authorized partners, or from a reliable mirror site. Skype may
also be safely downloaded from other locations, but in this case it is
particularly important that you verify the authenticity of the
download.
We recommend that once you download any Skype software that you verify
its integrity by the methods listed in Section 6 of this Bulletin.
x86 platform, Microsoft Windows 2000 or Microsoft Windows XP:
http://www.skype.com/download/skype/windows/
x86 platform, Linux: http://www.skype.com/download/skype/linux/
PPC and x86 platforms, Mac OS X v10.3.9 or later:
http://www.skype.com/download/skype/macosx/
Pocket PC platform, Microsoft Windows Mobile 2003:
http://www.skype.com/download/skype/pocketpc/
6. Authenticity verification
- Bulletin authenticity verification:
Skype security bulletins are published on Skype's web site and via
mailing lists. The authenticity and integrity of a Skype security
bulletins may be determined by inspecting the crypto- graphic
signature that is attached to each bulletin. All Skype security
bulletins are published with a valid digital signature produced by
PGP.
- Software authenticity verification:
Both the Skype installer program and the Skype program that is
installed by the installer are digitally signed.
For Skype software built for Microsoft Windows and Mac OSX operating
environments, the digital certificate used by Skype to sign software
packages is signed by "VeriSign Class 3 Code Signing 2004 CA".
For Skype software built for Linux platforms, all packages are signed
by PGP key ID 0xD66B746E, the public component of which may be
downloaded from http://www.skype.com/download/skype/linux/.
- For general information about Skype security, please visit the Skype
Security Resource Center at http://www.skype.com/security/.
7. Common Vulnerability Assessment System (CVSS) assessment
Skype has rated the issue covered by this Security Bulletin under the
CVSS scheme as follows:
Base metrics as of 2008-01-31:
Access Vector (AV) ........... Network
Access Complexity (AC) ....... Medium
Authentication (Au) .....,.... Multiple
Confidentiality Impact (C) ... Complete
Integrity Impact (I) ......... Complete
Availability Impact (A) ...... Complete
Computed CVSS base score: 7.8
Temporal metrics as of 2008-01-31
Exploitability (E) ........... proof-of-concept
Remediation Level (RL) ....... official-fix
Report Confidence (RC) ....... confirmed
Computed CVSS temporal score: 6.1
Skype participates in the CVSS by rating each identifiable security
vulnerability against the CVSS base metrics. In addition, Skype may
rate each vulnerability against temporal metrics from time to time. As
suggested by the name, temporal metrics for a particular vulnerability
may change from time to time.
More information about the CVSS may be obtained from the CVSS host
website at http://www.first.org/cvss/.
8. Credits and additional information
Skype would like to thank Aviv Raff for having referred this problem
to Skype in timely manner.
9. Bulletin release history
2008-01-31 Initial bulletin release
10. Notices
Copyright 2008 Skype Technologies, S.A. All rights reserved.
This Skype Security Bulletin may be reproduced and distributed,
provided that the Bulletin is not modified in any way and is
attributed to Skype Technologies, S.A. and provided that repro-
duction and distribution is performed for non-commercial purposes.
This Skype Security Bulltin is provided to you on an "AS IS" basis and
may contain information provided by third parties. Skype makes no
guarantees or warranties as to the information contained herein. ANY
AND ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR
NON-INFRINGEMENT, ARE HEREBY DISCLAIMED.
To report a security issue to Skype, please send an e-mail that
describes the problem or vulnerability to security@skype.com.
Please consider securing any reports that disclose security
vulnerabilities by encrypting them using the current PGP key of the
Skype Computer Emergency Response Team (SKY-CERT), PGP key ID
0xAD2DF320.
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The University of Queensland
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