NGSSoftware Insight Security Research Advisory

Name: Microsoft SQL Server Webtasks privilege elevation
Systems: Microsoft SQL Server 2000 and 7
Severity: High Risk
Vendor URL: http://www.microsoft.com/
Author: David Litchfield (david@ngssoftware.com)
Advisory URL: http://www.ngssoftware.com/advisories/mssql-webtasks.txt
Date: 17th October 2002
Advisory number: #NISR17102002


Description
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Using a number of flaws in the webtask functionality of Microsoft SQL Server
an attacker may gain control of the database by elevating their privileges.

Details
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The xp_runwebtask stored procedure fails to set permissions properly when
executed and runs with the privileges of the SQL Server. xp_runwebtask can
be executed by 'PUBLIC'.

The permissions of the table that stores webtasks, namely
msdb.dbo.mswebtasks, are set loosely allowing 'PUBLIC' to INSERT, UPDATE,
DELETE and SELECT.

By updating a webtask owned by the database owner and then running it
through xp_runwebtask an attacker may elevate their privileges. In terms of
exploitation an attacker may choose to run OS commands or add themselves to
the SYSADMIN group.


Fix Information
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NGSSoftware alerted Microsoft to these problems on the 23rd of August.
Microsoft has released a patch that addresses these issues. For more details
please see

http://www.microsoft.com/technet/treeview/?url=/technet/security/bulletin/MS
02-061.asp

A check and fix for these problems already exists in NGSSQuirreL, an
advanced SQL Server security management tool, of which more information
is available from the NGSSite: http://www.nextgenss.com/.