Vulnerability Note VU#696644

Microsoft SQL Server fails to properly validate parameters to the sp_replwritetovarbin extended stored procedure

Overview

A vulnerability in the Microsoft SQL Server sp_replwritetovarbin extended stored procedure could allow an authenticated attacker to execute arbitrary code on an affected server.

I. Description

Some versions of Microsoft SQL Server contain a vulnerability in the sp_replwritetovarbin stored procedure. The vulnerability could allow an attacker to modify heap memory and potentially execute arbitrary code. The vulnerability is described in SEC Consult Security Advisory < 20081209-0>. Microsoft Security Bulletin MS09-004 provides further details, including affected database versions and workarounds.

In order to access sp_replwritetovarbin, an attacker would need to authenticate to the database first. A separate SQL injection vulnerability in a web application could allow a remote, unauthenticated attacker to exploit the sp_replwritetovarbin vulnerability with the user credentials of the web application. Microsoft Security Advisory (954462) provides detection and mitigation advice for SQL injection vulnerabilities.

Exploit code is publicly available for this vulnerability.

II. Impact

A local or remote authenticated attacker may be able to execute arbitrary code with the privileges of the SQL Server on the affected system. In the case of a SQL injection vulnerability in a web application that uses a vulnerable database, a remote attacker may be able to exploit the sp_replwritetovarbin vulnerability with credentials of the web application.

III. Solution

Apply an update

This issue is addressed in Microsoft Security Bulletin MS09-004.
Workarounds

Deny execute permissions on sp_replwritetovarbin as described in Microsoft Security Bulletin MS09-004.

Alternatively, remove sp_replwritetovarbin using sp_dropextendedproc as described in SEC Consult Security Advisory < 20081209-0> and "Removing an Extended Stored Procedure from SQL Server."

Removing execute permissions or removing sp_replwritetovarbin may impact application functionality.

Systems Affected

Vendor	Status	Date Notified	Date Updated
Microsoft Corporation	Vulnerable	2008-12-19	2009-02-10

References

http://www.sec-consult.com/files/20081209_mssql-sp_replwritetovarbin_memwrite.txt
http://www.milw0rm.com/exploits/7501
http://www.microsoft.com/technet/security/advisory/961040.mspx
http://msdn.microsoft.com/en-us/library/aa215995(SQL.80).aspx
http://msdn.microsoft.com/en-us/library/aa933290(SQL.80).aspx
http://www.microsoft.com/technet/security/advisory/954462.mspx
http://www.microsoft.com/technet/security/bulletin/ms09-004.mspx

Credit

This vulnerability was reported by Bernhard Mueller of SEC Consult Vulnerability Lab.

This document was written by Chad R Dougherty and Art Manion.

Other Information

Date Public:	2008-12-09
Date First Published:	2008-12-24
Date Last Updated:	2009-02-10
CERT Advisory:
CVE-ID(s):	CVE-2008-5416
NVD-ID(s):	CVE-2008-5416
US-CERT Technical Alerts:	TA09-041A
Metric:	4.45
Document Revision:	18