mailing list archives
Microsoft Security Bulletin (MS99-053)
From: aleph1 () UNDERGROUND ORG (Aleph One)
Date: Thu, 2 Dec 1999 15:21:27 -0800
The following is a Security Bulletin from the Microsoft Product Security
Please do not reply to this message, as it was sent from an unattended
Microsoft Security Bulletin (MS99-053)
Patch Available for Windows "Multithreaded SSL ISAPI Filter" Vulnerability
Originally Posted: December 02, 1999
Microsoft has released a patch that eliminates a vulnerability in the SSL
ISAPI filter that ships with Microsoft(r) Internet Information Server and
is used by other Microsoft products. If called by a multi-threaded
application under very specific, and fairly rare, circumstances, a
synchronization error in the filter could allow a single buffer of plaintext
to be transmitted back to the data's owner.
Frequently asked questions regarding this vulnerability can be found at
The SSL ISAPI filter provided as part of IIS supports concurrent use. When
used in this mode, a synchronization problem could induce a race condition
and cause a single buffer of plaintext to be leaked. The conditions under
which this could happen are very rare, and could only occur when a single
user's session was multi-threaded and traffic volumes were extremely high.
The scope of this vulnerability is very limited. The leaked plaintext would
always be sent to its owner, never another user. Also, because the leaked
data would fail its integrity check, the effect of the leak would be to
cause the SSL session to immediately collapse. The condition could not be
induced by a hostile user, and would offer at best a target of opportunity.
Finally, it is worth noting that this vulnerability only affects the SSL
ISAPI filter, not the secure communications capability provided by Windows
NT via Schannel.
Affected Software Versions
- Microsoft IIS 4.0
- Microsoft Site Server 3.0
- Microsoft Site Server Commerce Edition 3.0
NOTE: This and other patches are available from the Microsoft
Download Center (http://www.microsoft.com/downloads/search.asp?
Please see the following references for more information related to this
- Microsoft Security Bulletin MS99-053: Frequently Asked Questions,
- Microsoft Knowledge Base (KB) article Q244613,
IIS 4.0 SSL ISAPI Filter Can Leak Single Buffer of Plaintext,
(Note: It may take 24 hours from the original posting of this
bulletin for this KB article to be visible.)
- Microsoft Security Advisor web site,
Obtaining Support on this Issue
This is a fully supported patch. Information on contacting Microsoft
Technical Support is available at
Microsoft acknowledges Wall Data for bringing this issue to our attention.
- December 02, 1999: Bulletin Created.
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.
You have received this e-mail bulletin as a result of your registration
to the Microsoft Product Security Notification Service. You may
unsubscribe from this e-mail notification service at any time by sending
an e-mail to MICROSOFT_SECURITY-SIGNOFF-REQUEST () ANNOUNCE MICROSOFT COM
The subject line and message body are not used in processing the request,
and can be anything you like.
For more information on the Microsoft Security Notification Service
please visit http://www.microsoft.com/security/services/bulletin.asp. For
security-related information about Microsoft products, please visit the
Microsoft Security Advisor web site at http://www.microsoft.com/security.
- Microsoft Security Bulletin (MS99-053) Aleph One (Dec 02)