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              AUSCERT External Security Bulletin Redistribution

           ESB-2001.049 -- Microsoft Security Bulletin (MS01-004)
                 Patch Available to Eliminate New Variant of
               "File Fragment Reading via .HTR" Vulnerability
                               8 February 2001

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

        AusCERT Security Bulletin Summary
        ---------------------------------

Product:                Internet Information Server 4.0
                        Internet Information Server 5.0
Vendor:                 Microsoft
Impact:                 Read-only Data Access
Access Required:        Remote

Ref:                    ESB-2000.088
                        ESB-2000.175

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- - -
Title:      Patch Available to Eliminate New Variant of "File
            Fragment Reading via .HTR" Vulnerability
Date:       29 January 2001
Software:   IIS 4.0 and 5.0
Impact:     File Reading
Bulletin:   MS01-004
KB Article: Q285985 (available soon)

Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/ms01-004.asp
- - ----------------------------------------------------------------------

Issue:
======
This vulnerability involves a new variant of the "File Fragment
Reading via .HTR" vulnerability, previous variants of which were
discussed in Microsoft Security Bulletins MS00-031 and MS00-044. Like
the original variants, this one could enable an attacker to request a
file in a way that would cause it to be processed by the .HTR ISAPI
extension. The result of doing this is that fragments of server-side
files like .ASP files could potentially be sent to the attacker.
There is no capability via the vulnerability to add, change or delete
files on the server, or to access a file without permissions.

Mitigating Factors:
====================
 - Microsoft has long recommended that customers disable the .HTR
   functionality unless there is a business-critical reason not to.
   Customers who have followed this recommendation would be at no
   risk from this vulnerability.
 - Best practices strongly recommend against ever including sensitive
   information in .ASP and other server-side files.  If this
   recommendation has been followed, there would be no sensitive
   information in the file to compromise.
 - The .HTR processing would tend to strip out the sections of the
   file most likely to contain sensitive information.
 - There would need to be zeros located fortuitously in memory to
   serve as null terminators for the data.

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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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