Vulnerability Note VU#370308

Microsoft SQL Server 2000 contains denial-of-service vulnerability in SQL Server Resolution Service

Overview

Microsoft SQL Server 2000 contains a vulnerability that allows remote attackers to create a denial-of-service condition between two Microsoft SQL servers.

I. Description

The SQL Server Resolution Service (SSRS) was introduced in Microsoft SQL Server 2000 to provide referral services for multiple server instances running on the same machine. The service listens for requests on UDP port 1434 and returns the address and port number of the SQL server instance that provides access to the requested database.

In addition to providing referrals, the SSRS is capable of replying to "ping" messages from other SQL servers to confirm its presence on a network. When the service receives such a message, it replies to the transmitting host with an identical reply message. In normal operation, the SSRS service is responsible for replying to ping messages sent by an SQL Server and does not initiate them. However, an attacker can create a forged ping message to one instance of the SSRS (Victim A, port 1434) that appears to originate from another instance (Victim B, port 1434), causing Victim A and Victim B to continuously exchange messages. This cycle will continue to consume server and network resources until one of the servers stops sending packets for one of several reasons, including a restart of the SQL Server, a reboot of the server host, or a network failure.

II. Impact

This vulnerability allows remote attackers to initiate a denial-of-service attack between two Microsoft SQL servers.

III. Solution

Apply a patch

This vulnerability was originally addressed by Microsoft in Security Bulletin MS02-039. In January 2003, Microsoft updated MS02-039 to recommend that customers apply the patch from Microsoft Security Bulletin MS02-061, which addresses additional vulnerabilities. For more information, please see

http://www.microsoft.com/technet/security/bulletin/MS02-039.asp

http://www.microsoft.com/technet/security/bulletin/MS02-061.asp

This vulnerability also affects any products that include the Microsoft Desktop Engine (MSDE) 2000. For more information, please see

http://www.microsoft.com/technet/security/MSDEapps.asp

Block port 1434/udp

As a workaround, system administrators can use a firewall to block port 1434/udp at an appropriate network border, thus preventing external attackers from exploiting this vulnerability.

Systems Affected

Vendor	Status	Date Updated
Cisco Systems Inc.	Vulnerable	27-Jan-2003
Microsoft Corporation	Vulnerable	25-Jul-2002

References

CA-2003-04, CA-1996-01,CA-1996-21
http://www.microsoft.com/technet/security/bulletin/MS02-039.asp
http://www.microsoft.com/technet/security/MSDEapps.asp
http://www.microsoft.com/technet/security/virus/alerts/slammer.asp
http://support.microsoft.com/support/misc/kblookup.asp?id=Q323875
http://www.microsoft.com/technet/prodtechnol/sql/maintain/security/sql2ksec.asp
http://www.nextgenss.com/advisories/mssql-udp.txt
http://www.nextgenss.com/vna/ms-sql.txt
http://www.securityfocus.com/bid/5312
http://www.cert.org/advisories/CA-1996-01.html
http://www.cert.org/advisories/CA-1996-21.html
http://www.cert.org/advisories/CA-2003-04.html

Credit

The CERT/CC thanks Microsoft for the information provided in their advisory and NGSSoftware for their discovery and analysis of this vulnerability.

This document was written by Jeffrey P. Lanza.

Other Information

Date Public	07/24/2002
Date First Published	07/26/2002 02:03:17 PM
Date Last Updated	02/05/2003
CERT Advisory
CVE Name	CAN-2002-0650
US-CERT Technical Alerts
Metric	5.32
Document Revision	46

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