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Title:      SQL Extended Procedure Functions Contain Unchecked
            Buffers (Q319507)
Date:       17 April 2002
Software:   Microsoft SQL Server
Impact:     Run Code of Attacker's Choice
Max Risk:   Moderate
Bulletin:   MS02-020

Microsoft encourages customers to review the Security Bulletin at: 
http://www.microsoft.com/technet/security/bulletin/MS02-020.asp.
- ----------------------------------------------------------------------

Issue:
======
SQL Server 7.0 and 2000 provide for extended stored procedures,
which are external routines written in a programming language such
as C. These procedures appear to users as normal stored procedures
and are executed in the same way. SQL Server 7.0 and 2000 include
a number of extended stored procedures which are used for various
helper functions 

Several of the Microsoft-provided extended stored procedures have
a flaw in common - namely, they fail to perform input validation
correctly, and are susceptible to buffer overruns as a result
exploiting the flaw could enable an attacker to either cause the
SQL Server service to fail, or to cause code to run in the security
context in which SQL Server is running. SQL Server can be
configured to run in various security contexts, and by default
runs as a domain user. The precise privileges the attacker could
gain would depend on the specific security context that the
service runs in. 

An attacker could exploit this vulnerability in one of two ways.
Firstly, the attacker could attempt to load and execute a database
query that calls one of the affected functions. Secondly, if a
web-site or other database front-end were configured to access
and process arbitrary queries, it could be possible for the 
attacker to provide inputs that would cause the query to call
one of the functions in question with the appropriate
malformed parameters.

Mitigating Factors:
====================
 - The effect of exploiting the vulnerability would depend on the
   specific configuration of the SQL Server service. SQL Server can
   be configured to run in a security context chosen by the
   administrator. By default, this context is as a domain user.
   If the rule of least privilege has been followed, it would
   minimize the amount of damage an attacker could achieve. 

 - The vector for exploiting this vulnerability could be blocked
   by following best practices. Specifically, untrusted users should
   not be able to load and execute queries of their choice on a
   database server. In addition, publicly accessible database
   queries should filter all inputs prior to processing.

Risk Rating:
============
 - Internet systems: Moderate
 - Intranet systems: Moderate
 - Client systems: Moderate

Patch Availability:
===================
 - A patch is available to fix this vulnerability. Please read the 
   Security Bulletin at
   http://www.microsoft.com/technet/security/bulletin/ms02-020.asp
   for information on obtaining this patch.


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