Another way to crash NT DNS server.

Date: Tue, 10 Jun 1997 18:31:53 -0500
From: Aleph One <aleph1@DFW.NET>
To: BUGTRAQ@NETSPACE.ORG
Subject: Q169461: Access Violation in DNS.EXE Caused by Malicious Telnet              Attack

DOCUMENT:Q169461    [winnt]
TITLE: Access Violation in DNS.EXE Caused by Malicious Telnet Attack
PRODUCT: Microsoft Windows NT
PROD/VER:4.00
OPER/SYS:WINDOWS
KEYWORDS:kbbug4.00 kbnetwork NTSrv nttcp

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The information in this article applies to:

 - Microsoft Windows NT Server version 4.0
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SYMPTOMS
========

You may receive an Access Violation in Dns.exe. This is most often occurs
on computers connected to public networks, such as the Internet, where
deliberate attacks are common.

CAUSE
=====

This particular attack is usually generated maliciously by typing the
following command on the attacking system:

   telnet <mycomputer> 19 | telnet <mycomputer> 53

This command causes a telnet connection to be established to port 19 (the
chargen service, which generates a string of characters) with the output
redirected to a telnet connection to port 53 (the DNS service.) This flood
of characters causes an Access Violation in the DNS service, which is
terminated, disrupting name resolution services.

RESOLUTION
==========

The Microsoft DNS Server has been modified to to correct this problem.
Obtain the following fix or wait for the next Windows NT service pack.

This hotfix has been posted to the following Internet location:

   ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/NT40/
   hotfixes-postSP3/dns-fix

STATUS
======

Microsoft has confirmed this to be a problem in Windows NT version 4.0.
A supported fix is now available, but has not been fully regression-tested
and should be applied only to systems experiencing this specific problem.
Unless you are severely impacted by this specific problem, Microsoft
recommends that you wait for the next Service Pack that contains this fix.
Contact Microsoft Technical Support for more information.

Additional reference words: 4.00 prodnt denial of service dns telnet port
53

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