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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
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.
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.
for information on obtaining this patch.
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