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 affected servers.

III. Solution

Apply a patch


Microsoft has published Security Bulletin MS02-039 to address this vulnerability. For more information, please see


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

VendorStatusDate Updated
Microsoft CorporationVulnerable25-Jul-2002

References



http://www.microsoft.com/technet/security/bulletin/MS02-039.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.tx
http://www.securityfocus.com/bid/5312
http://www.cert.org/advisories/CA-1996-01.html
http://www.cert.org/advisories/CA-1996-21.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 Public07/24/2002
Date First Published07/26/2002 02:03:17 PM
Date Last Updated07/29/2002
CERT Advisory 
CVE NameCAN-2002-0650
Metric5.32
Document Revision34

CERT Copyright Material