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AUSCERT External Security Bulletin Redistribution
ESB-2003.0188 -- Microsoft Security Bulletin MS03-009
Flaw In ISA Server DNS Intrusion Detection Filter Can Cause
Denial Of Service (331065)
20 March 2003
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: ISA Server 2000
Vendor: Microsoft
Operating System: Windows
Impact: Denial of Service
Access Required: Remote
CVE Names: CAN-2003-0011
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Title: Flaw In ISA Server DNS Intrusion Detection Filter Can
Cause Denial Of Service (331065)
Date: 19 March 2003
Software: Microsoft ISA Server
Impact: Denial of Service
Max Risk: Moderate
Bulletin: MS03-009
Microsoft encourages customers to review the Security Bulletins at:
http://www.microsoft.com/technet/security/bulletin/MS03-009.asp
http://www.microsoft.com/security/security_bulletins/ms03-009.asp
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Issue:
======
Microsoft Internet Security and Acceleration (ISA) Server 2000
contains the ability to apply application filters to incoming
traffic. Application filters allow ISA Server to analyze a data
stream for a particular application and provide application-
specific processing including inspecting, screening or blocking,
redirecting, or modifying the data as it passes through the
firewall. This mechanism is used to protect against invalid URLs
which may indicate attempted attacks as well as attacks against
internal Domain Name Service (DNS) Servers.
A flaw exists in the ISA Server DNS intrusion detection application
filter, and results because the filter does not properly handle a
specific type of request when scanning incoming DNS requests.
An attacker could exploit the vulnerability by sending a specially
formed request to an ISA Server computer that is publishing a DNS
server, which could then result in a denial of service to the
published DNS server. DNS requests arriving at the ISA Server would
be stopped at the firewall, and not passed through to the internal
DNS server. All other ISA Server functionality would be unaffected.
Mitigating Factors:
====================
- By default, no DNS servers are published. DNS server publishing
must be manually enabled.
- The vulnerability would not enable an attacker to gain any
privileges on an affected ISA Server or the published DNS server
or to compromise any cached content on the server. It is
strictly a denial of service vulnerability.
Risk Rating:
============
- Moderate
Patch Availability:
===================
- A patch is available to fix this vulnerability. Please read the
Security Bulletins at
http://www.microsoft.com/technet/security/bulletin/ms03-009.asp
http://www.microsoft.com/security/security_bulletins/ms03-009.asp
for information on obtaining this patch.
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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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