RE: Fw: Microsoft Security Bulletin MS02-027
- From: "Walkowiak, Matt" <Matt.Walkowiak@xxxxxxxxxxxx>
- To: "[ISAserver.org Discussion List]" <isalist@xxxxxxxxxxxxx>
- Date: Wed, 12 Jun 2002 13:53:33 -0500
One other thing that needs mentioning - if you want to block this at
your Firewall (or if ISA is acting strictly like a dumb firewall, not
proxying anything) you will need to block TCP packets on SOURCE port 70
(Incoming), as opposed to DESTINATION port 70 (Outgoing). The Gopher
packets are coming from port 70 (the gopher server) and hitting your
computer, the victim, on a random destination port.
Of course, if you block port 70 in both directions, that's good, too.
Oh, and if your firewall uses rules in a specific order (well, they
pretty much all do, but for the ones that you have control over the
order like Iptables or Firewall-1) make sure you block port 70 BEFORE
any masquerade rule - if your inside computers establish the connection
to a bad gopher server, your port 70 rule would never get affected
because the return packets would have a successful hit on the Masq rule
and never see your port 70 rule.
Matt Walkowiak
-----Original Message-----
From: Jim Harrison [mailto:jim@xxxxxxxxxxxx]
Sent: Tuesday, June 11, 2002 7:18 PM
To: [ISAserver.org Discussion List]
Subject: [isalist] Fw: Microsoft Security Bulletin MS02-027
http://www.ISAserver.org
Pay close attention to this one, folks!
Jim Harrison
MCP(NT4, W2K), A+, Network+, PCG
http://isaserver.org/authors/harrison/
Read the books!
----- Original Message -----
From: "Jerry Bryant [MS]" <jbryant@xxxxxxxxxxxxxxxxxxxx>
Newsgroups:
microsoft.public.security,microsoft.public.isa,microsoft.public.isaserve
r,mi
crosoft.public.windows.inetexplorer.ie55.browser,microsoft.public.window
s.in
etexplorer.ie6.browser
Sent: Tuesday, June 11, 2002 4:40 PM
Subject: Microsoft Security Bulletin MS02-027
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.
- ----------------------------------------------------------------------
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.
- ---------------------------------------------------------------------
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
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BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR
ITS
SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME
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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.
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