INFORMATION BULLETIN
INFORMATION BULLETIN
| PROBLEM: | The idq.dll extension contains a buffer overflow in the code handling input URLs. |
| PLATFORM: | Windows NT, 2000; affects IIS web servers: Index Server 2.0 and Indexing Service. |
| DAMAGE: | The idq.dll executes in the system context, therefore this exploit could result in Administrator compromise, allowing the attacker to execute code of his/her choice. |
| SOLUTION: | Apply the patches described in Microsoft's bulletin immediately. |
| VULNERABILITY ASSESSMENT: |
VERY HIGH. This vulnerability is remotely exploitable, and can result in total system or Administrator compromise. |
[****** Start Microsoft Advisory ******]
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Title: Unchecked Buffer in Index Server ISAPI Extension Could
Enable Web Server Compromise
Date: 18 June 2001
Software: Index Server 2.0 and Indexing Service
Impact: Run code of attacker's choice
Bulletin: MS01-033
Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS01-033.asp.
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Issue:
======
As part of its installation process, IIS installs several ISAPI extensions -- .dlls
that provide extended functionality. Among these is idq.dll, which is a component
of Index Server (known in Windows 2000 as Indexing Service) and provides support
for administrative scripts (.ida files) and Internet Data Queries (.idq files).
A security vulnerability results because idq.dll contains an unchecked buffer in a
section of code that handles input URLs. An attacker who could establish a web session
with a server on which idq.dll is installed could conduct a buffer overrun attack
and execute code on the web server. Idq.dll runs in the System context, so exploiting
the vulnerability would give the attacker complete control of the server and allow him
to take any desired action on it.
The buffer overrun occurs before any indexing functionality is requested. As a result,
even though idq.dll is a component of Index Server/Indexing Service, the service would
not need to be running in order for an attacker to exploit the vulnerability. As long
as the script mapping for .idq or .ida files were present, and the attacker were able
to establish a web session, he could exploit the vulnerability.
Clearly, this is a serious vulnerability, and Microsoft urges all customers to take
action immediately. Customers who cannot install the patch can protect their systems
by removing the script mappings for .idq and .ida files via the Internet Services
Manager in IIS. However, as discussed in detail in the FAQ, it is possible for these mappings
to be automatically reinstated if additional system components are added or removed. Because
of this, Microsoft recommends that all customers using IIS install the patch, even if the script
mappings have been removed.
Mitigating Factors:
====================
- The vulnerability can only be exploited if a web session
can be established with an affected server. Customers
who have installed Index Server or Index Services but not
IIS would not be at risk. This is the default case for
Windows 2000 Professional.
- The vulnerability cannot be exploited if the script mappings
for Internet Data Administration (.ida) and Internet Data
Query (.idq) files are not present. The procedure for
removing the mappings is discussed in the IIS 4.0
(http://www.microsoft.com/technet/security/iischk.asp) and IIS
5.0 (http://www.microsoft.com/technet/security/iis5chk.asp)
Security checklists, can be automatically removed via either
the High Security Template or the Windows 2000 Internet Server
Security Tool (http://www.microsoft.com/technet/security/tools.asp).
Customers should be aware, however, that subsequently adding
or removing system components can cause the mapping to be
reinstated, as discussed in the FAQ.
- An attacker's ability to extend control from a compromised web
server to other machines would depend heavily on the specific
configuration of the network. Best practices recommend that the
network architecture account for the inherent high-risk that
machines in an uncontrolled environment, like the Internet,
face by minimizing overall exposure though measures like DMZ's,
operating with minimal services and isolating contact with
internal networks. Steps like this can limit overall exposure
and impede an attacker's ability to broaden the scope of a
possible compromise.
Patch Availability:
===================
- A patch is available to fix this vulnerability. Please read the
Security Bulletin
http://www.microsoft.com/technet/security/bulletin/ms01-033.asp
for information on obtaining this patch.
Acknowledgment:
===============
- eEye Digital Security (http://www.eeye.com)
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[****** End Microsoft Advisory ******]
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