Microsoft Security Bulletin MS03-009: Flaw In ISA Server DNS IntrusionDetection Filter Can Cause Denial Of Service (331065) (fwd)

Dave Ahmad <da@securityfocus.com> · Thu, 20 Mar 2003 09:04:51 -0700 (MST)

David Mirza Ahmad
Symantec

"sabbe dhamma anatta"

0x26005712
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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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