Microsoft Security Bulletin MS02-028

From: Jerry Bryant [MS] (jbryant@online.microsoft.com)
Date: 06/13/02 

From: "Jerry Bryant [MS]" <jbryant@online.microsoft.com>
Date: Wed, 12 Jun 2002 16:17:51 -0700

Title: Heap Overrun in HTR Chunked Encoding Could Enable Web
            Server Compromise (Q321599)
Date: 12 June 2002
Software: Internet Information Server
Impact: Run Code of Attacker's Choice
Max Risk: Moderate
Bulletin: MS02-028

Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS02-028.asp.
- ----------------------------------------------------------------------

Issue:
======
This patch eliminates a newly discovered vulnerability affecting Internet
Information Services. Although Microsoft typically delivers cumulative
patches for IIS, in this case we have delivered a patch that eliminates only
this new vulnerability, while completing a cumulative patch. When the
cumulative patch is customer-ready, we will update this bulletin with
information on its availability. The FAQ provides information on the
circumstances surrounding the vulnerability, and why we believe releasing a
singleton patch immediately is in customers' best interests. To ensure that
servers are fully protected against past as well as current vulnerabilities,
we strongly recommend installing the previous cumulative patch (discussed in
Microsoft Security Bulletin MS02-018) before
installing this patch.

The vulnerability is similar to the first vulnerability discussed in
Microsoft Security Bulletin MS02-018. Like that vulnerability, this one
involves a buffer overrun in the Chunked Encoding data transfer mechanism in
IIS 4.0 and 5.0, and could likewise be used to overrun heap memory on the
system, with the result of either causing the IIS service to fail or
allowing code to be run on the server. The chief difference between the
vulnerabilities is that the newly discovered one lies in the ISAPI extension
that implements HTR - an older, largely obsolete scripting technology -
where the previous one lay in the ISAPI extension that implements ASP.

Mitigating Factors:
====================
 - Microsoft has long recommended disabling HTR functionality
   unless there is a business-critical reason for retaining it.
   Systems on which HTR is disabled would not be at risk from this
   vulnerability.

 - The IIS Lockdown Tool disables HTR by default in all server
   configurations.

 - The current version of the URLScan tool provides a means of
   blocking chunked encoding transfer requests by default.

 - On default installations of IIS 5.0, exploiting the
   vulnerability to run code would grant the attacker the privileges
   of the IWAM_computername account, which has only the privileges
   commensurate with those of an interactively logged-on
   unprivileged user.

Risk Rating:
============
 - Internet systems: Moderate
 - Intranet systems: Moderate
 - Client systems: Moderate

Patch Availability:
===================
 - A patch is available to fix this vulnerability. Please read the
   Security Bulletin at
   http://www.microsoft.com/technet/security/bulletin/ms02-028.asp
   for information on obtaining this patch.

Acknowledgment:
===============
 - eEye Digital Security (http://www.eeye.com/)

- ---------------------------------------------------------------------

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. 

--
Regards,
Jerry Bryant - MCSE, MCDBA
Microsoft IT Communities
Get Secure! www.microsoft.com/security
This posting is provided "AS IS" with no warranties, and confers no rights.

Relevant Pages

  • Re: [Full-disclosure] Security Alert: Unofficial IE patches appear on internet
    ... created by a vulnerability is as serious as this case and the available ... Microsoft will be inclined strongly against holding on to this patch. ... Microsoft often have patches ready but wait for the corporate known ...
    (Full-Disclosure)
  • Re: NT4 patch for MS00-084??
    ... there is no such patch to be found on the technet security ... > "Microsoft has released a patch that eliminates a security ... > vulnerability in Microsoft® Indexing Services for Windows 2000. ...
    (microsoft.public.security)
  • Re: ??? MS03-040 Cumulative Patch for Internet Explorer (828750) ???
    ... > Does it fix this object data tag vulnerability or not? ... > This is a flaw in Microsoft's primary contribution to HTML, ... > only **doesn't** fix that vulnerability, Microsoft dont even acknowledge ... > The patch addresses the vulnerabilities by ensuring that Internet ...
    (microsoft.public.windowsxp.security_admin)
  • Virus or from Microsoft?
    ... this communication is being sent to all of our Microsoft ... to alert you of this Security Bulletin. ... and a patch regarding a vulnerability in the ... likelihood of the exploitation of this vulnerability. ...
    (microsoft.public.windowsxp.security_admin)
  • Microsoft Security Bulletin MS01-055 (Version 2.0)
    ... The following is a Security Bulletin from the Microsoft Product Security ... The third vulnerability is a new variant of a vulnerability ...
    (Bugtraq)