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AUSCERT External Security Bulletin Redistribution
ESB-2003.0778 -- Microsoft Security Bulletin MS02-050 (REVISED)
Certificate Validation Flaw Could Enable Identity Spoofing
13 November 2003
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AusCERT Security Bulletin Summary
---------------------------------
Publisher: Microsoft
Operating System: Windows 2000
Impact: Provide Misleading Information
Access Required: Remote
Ref: ESB-2002.490
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Title: Certificate Validation Flaw Could Enable Identity
Spoofing (329115)
Date: September 4,2002 (Revised November 11, 2003)
Software: Microsoft Windows 98
Microsoft Windows 98 Second Edition
Microsoft Windows Me
Microsoft Windows NT(r) 4.0
Microsoft Windows NT 4.0, Terminal Server Edition
Microsoft Windows 2000
Microsoft Windows XP
Microsoft Office for Mac
Microsoft Internet Explorer for Mac
Microsoft Outlook Express for Mac
Impact: Identity spoofing and, in some cases, ability to gain
control over a user's system.
Max Risk: Important
Bulletin: MS02-050
Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS02-050.asp
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Reason for Revision:
====================
Microsoft re-issued this security bulletin on November 11, 2003 to
advise on the availability of an updated Microsoft Windows 2000
Service Pack 4 (SP4) security patch. This revised security patch
corrects a regression that may occur during the installation of
Microsoft Internet Explorer 6.0 Service Pack 1 on Windows 2000 SP4.
This regression removes the update that is discussed in this bulletin
and that is provided as part of Windows 2000 SP4. Customers who are
using Windows 2000 SP4 and then installed Internet Explorer 6.0
Service Pack 1 should apply the updated Windows 2000 SP4 security
patch to help protect from this vulnerability.
Issue:
======
The vulnerability identified in the original version of the bulletin
could enable an attacker who had a valid end-entity certificate to
issue a subordinate certificate that, although bogus, would
nevertheless pass validation. Because CryptoAPI is used by a wide
range of applications, this could enable a variety of identity
spoofing attacks.
Mitigating Factors:
====================
* The user could always manually check a certificate chain, and
might notice in the case of a spoofed chain that there was an
unfamiliar intermediate CA.
* Unless the attacker's digital certificates were issued by a CA
in the user's trust list, the certificate would generate a
warning when validated.
* The attacker could only spoof certificates of the same type as
the one he or she possessed. In the case where the attacker
attempted an attack using a high-value certificate such as
Authenticode certificates, this would necessitate obtaining a
legitimate certificate of the same type - which could require
the attacker to prove his or her identity or entitlement to the
issuing CA.
Risk Rating:
============
- Important
Patch Availability:
===================
- A patch is available to fix this vulnerability. Please read the
Security Bulletin at
http://www.microsoft.com/technet/security/bulletin/MS02-050.asp
for information on obtaining this patch.
Acknowledgment:
===============
- UK National Infrastructure Security Co-ordination Centre (NISCC)
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THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS
ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE
FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION 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.
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