Microsoft offers plug for 'critical' SQL Server holes

Microsoft Corp. warned of five vulnerabilities in its SQL Server 2000 database product, the most serious of which could allow an attacker to take over the server.

Deemed "critical" are three vulnerabilities in a feature that allows users to host multiple copies of SQL Server on a single machine. Less serious are two flaws in utilities for database consistency checks and database replication, Microsoft of Redmond, Washington, said in two security bulletins released late Wednesday.

Two buffer overrun flaws exist in the SQL Server Resolution Service, which is used to direct users to the right TCP (Transmission Control Protocol) port when multiple SQL Server copies are installed on one system. An attacker could get full control over the system the database software is running on by exploiting these flaws, Microsoft said.

A third flaw in the SQL Server Resolution Service is a denial of service vulnerability. An attacker could initiate a never-ending cycle of data packet exchanges between two or more database servers by sending a specially crafted data packet to a mechanism designed to check if a database server is online. The packet exchanges would consume most if not all of the server resources, slowing performance, Microsoft said.

Previous versions of SQL Server are not vulnerable as they do not support multiple copies on one system and thus do not include the SQL Server Resolution Service, Microsoft said.

Anybody with access to the SQL Server, for example via the Internet, could exploit the flaws in the Resolution Service, Microsoft said. That makes those flaws more serious than the flaws in the database consistency check and replication tools, which can only be exploited by registered database users and administrators.

A buffer overrun vulnerability exists in several Database Consistency Checkers that are part of database maintenance tools. A user assigned the already privileged db_owner or db_ddladmin role on one database could exploit the flaw to gain control over the complete server, Microsoft said.

The database replication function has a so-called SQL Injection Vulnerability that could allow an attacker to gain control over the server. It is exploitable by anybody with user privileges on the SQL server, but requires a special purpose user account to be enabled. This SQL Server Agent Proxy Account is disabled by default and can only be enabled by a server administrator, Microsoft said.

Patches to fix the vulnerabilities are available from Microsoft's TechNet Web site. Users should immediately patch the SQL Server Resolution Service holes, while the other patch should be considered, Microsoft said.

More information on the SQL Server Resolution Service vulnerabilities can be found at: information on the vulnerabilities in the SQL Server 2000 utilities can be found at:

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Joris Evers

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