Protect yourself against future threats.
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===========================================================================
AUSCERT External Security Bulletin Redistribution
ESB-2002.277 -- Microsoft Security Bulletin MS02-027
Unchecked Buffer in Gopher Protocol Handler Can Run Code
of Attacker's Choice (Q323889)
12 June 2002
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Internet Explorer
Proxy Server 2.0
Internet Security and Acceleration Server 2000
Vendor: Microsoft
Operating System: Windows
Impact: Execute Arbitrary Code/Commands
Access Required: Remote
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Title: Unchecked Buffer in Gopher Protocol Handler Can Run Code
of Attacker's Choice (Q323889)
Date: 11 June 2002
Software: Internet Explorer, Proxy Server, Internet Security and
Acceleration Server
Impact: Run Code of Attacker's Choice
Max Risk: Critical
Bulletin: MS02-027
Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS02-027.asp.
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Issue:
======
This is a work-around bulletin that details steps customers can
take to protect themselves against a publicly disclosed
vulnerability until patches are available.
The Gopher protocol is a legacy protocol that provides for the
transfer of text-based information across the Internet.
Information on Gopher servers is hierarchically presented using a
menu system, and multiple Gopher servers can be linked together to
form a collective "Gopherspace".
There is an unchecked buffer in a piece of code which handles the
response from Gopher servers. This code is used independently in
IE, ISA, and Proxy Server. A security vulnerability results
because it is possible for an attacker to attempt to exploit this
flaw by mounting a buffer overrun attack through a specially
crafted server response. The attacker could seek to exploit the
vulnerability by crafting a web page that contacted a server
under the attacker's control. The attacker could then either post
this page on a web site or send it as an HTML email. When the page
was displayed and the server's response received and processed,
the attack would be carried out.
A successful attack requires that the attacker be able to send
information to the intended target using the Gopher protocol.
Anything which inhibited Gopher connectivity could protect against
attempts to exploit this vulnerability. In the case of IE, the
code would be run in the user's context. As a result, any
limitations on the user would apply to the attacker's code
as well.
Mitigating Factors:
====================
- A successful attack requires that the attacker's server be
able to deliver information to the target using the Gopher
protocol. Customers who block Gopher at the perimeter would be
protected against attempts to exploit this vulnerability across
the Internet.
- In the case of IE, code would run in the security context of
the user. As a result, any limitations on the user's ability
would also restrict the actions an attacker's code could take.
- A successful attack against ISA and Proxy servers would
require that the malicious response be received by the web
proxy service. In practical terms, this means that a proxy
client would have to submit the initial request through the
proxy server.
Risk Rating:
============
- Internet systems: Critical
- Intranet systems: Critical
- Client systems: Critical
Patch Availability:
===================
- A patch is currently under development to fix this
vulnerability. Please read the Security Bulletin at
http://www.microsoft.com/technet/security/bulletin/ms02-027.asp
for workaround information while patches are developed.
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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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