iDefense Security Advisory 07.08.08: Microsoft SQL Server Restore Integer Underflow Vulnerability

iDefense Security Advisory 07.08.08
http://labs.idefense.com/intelligence/vulnerabilities/
Jul 08, 2008

I. BACKGROUND

SQL Server is Microsoft's database server product. It supports the
restoration and inspection of backups via SQL statements. For more
information see the vendor's website found at the following URL.

http://www.microsoft.com/sql/default.mspx

II. DESCRIPTION

Remote exploitation of an integer underflow vulnerability within
Microsoft Corp.'s SQL Server could allow a remote attacker to execute
arbitrary code with the privileges of the SQL Server.

The vulnerability exists within the code responsible for parsing a
stored backup file. A 32-bit integer value, representing the size of a
record, is taken from the file and used to calculate the number of
bytes to read into a heap buffer. This calculation can underflow, which
leads to insufficient memory being allocated. The buffer is subsequently
overfilled leading to an exploitable condition.

III. ANALYSIS

Exploitation of this vulnerability results in the execution of arbitrary
code with the privileges of the SQL Server. SQL Server 2005 runs under
the "NETWORK SERVICE" account, which is similar to an unprivileged user
account.

The target function can be run by any user with access to query the
database. This attack could also be conducted anonymously through a Web
application if it contained an SQL Injection vulnerability.

For the server to load the corrupted backup file, an attacker would have
to supply a path to a remote file using either SMB or WebDAV.

IV. DETECTION

iDefense confirmed the existence of this vulnerability in Microsoft SQL
Server 2005 Service Pack 2 Hot Fix 4. Additional tests against SQL
Server 2005 without any updates suggest it is also vulnerable. Previous
versions are also suspected to be vulnerable.

V. WORKAROUND

iDefense is currently unaware of any direct workaround for this issue.
Administrators can disable SMB and WebDAV support on affected SQL
Servers to prevent access to remote files.

VI. VENDOR RESPONSE

Microsoft has officially addressed this vulnerability with Security
Bulletin MS08-040. For more information, consult their bulletin at the
following URL.

http://www.microsoft.com/technet/security/bulletin/ms08-040.mspx

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2008-0107 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org/), which standardizes names for
security problems.

VIII. DISCLOSURE TIMELINE

12/06/2007 Initial vendor notification
12/06/2007 Initial vendor response
07/08/2008 Coordinated public disclosure

IX. CREDIT

This vulnerability was reported to iDefense by Brett Moore, from
Insomnia Security, [email protected] www.insomniasec.com

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X. LEGAL NOTICES

Copyright © 2008 iDefense, Inc.

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Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct,
indirect, or consequential loss or damage arising from use of, or
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