June 14th, 2002, 06:22 AM
Vulnerability: Microsoft SQLXML ISAPI Overflow and Cross Site Scripting
SQLXML allows XML data to be transferred to and from SQL Server, returning database queries as XML.
SQlXML has two vulnerabilities: a buffer overflow in the SQLXML ISAPI filter, and a cross site scripting vulnerability.
More complete details on how SQLXML works can be found in Microsoft's advisory (see below).
Cross Site Scripting
Part of the functionality of SQLXML is being able to run SQL queries via a URL such as:
This will return an XML document containing the query results.
It is possible to specify an extra parameter in the query, 'root', which returns the data as above, but with a 'root' tag of the xml document as the user specified.
This feature can be used to perform cross site scripting attacks against the web application running on the server:
Best practice recommends against allowing ad hoc URL queries against a database.
SQLXML ISAPI Filter Buffer Overflow
When making SQL queries using the 'sql=' functionality of SQLXML it is possible to specify certain parameters which affect the returned XML (e.g. xsl=). One of these parameters lets you set a content-type.
It's possible to crash IIS by requesting an overly long string in the ?contenttype= parameter. This could also allow arbitrary code to be run on the server in the context of the SYSTEM account.
A normal request looks like (in this case, a direct sql= query):
By specifying >240 characters for the content-type parameter it is possible to make inetinfo.exe crash.
E.g. (using a 'template' file rather than a direct query, in this case):
Microsoft has released patches and an advisory for the identified issues.
These are available from:
This advisory is available online at: