Microsoft Security Bulletin MS02-033

Technical description:

Commerce Server 2000 and Commerce Server 2002 are web server products for building e-commerce sites. These products provides tools and features that simplify developing and deploying e-commerce solutions, and provide tools that let the site administrator analyze the usage of their e-commerce site.

Four vulnerabilities exist in the Commerce Server products:

• A vulnerability that results because the Profile Service contains an unchecked buffer in a section of code that handles certain types of API calls. The Profile Service can be used to enable users to manage their own profile information and to research the status of their order. An attacker who provided specially malformed data to certain calls exposed by the Profile Service could cause the Commerce Server process to fail, or could run code in the LocalSystem security context. This vulnerability only affects Commerce Server 2000.
• A buffer overrun vulnerability in the Office Web Components (OWC) package installer used by Commerce Server. An attacker who provided specially malformed data as input to the OWC package installer could cause the process to fail, or could run code in the LocalSystem security context. This vulnerability only affects Commerce Server 2000.
• A vulnerability in the Office Web Components (OWC) package installer used by Commerce Server. An attacker who invoked the OWC package installer in a particular manner could cause commands to be run on the Commerce Server according to the privileges associated with the attacker's log on credentials. This vulnerability only affects Commerce Server 2000.
• A new variant of the ISAPI Filter vulnerability discussed in Microsoft Security Bulletin MS02-010. This variant affects both Commerce Server 2000 and Commerce Server 2002.

Mitigating factors:

Profile Service buffer overrun:

• The affected API calls in the Profile Service are not exposed to the Internet by default. The administrator must set up a Commerce Server site and include Profile Service calls as part of that site.
• The URLscan tool, if deployed using the default ruleset for Commerce Server, would make it difficult if not impossible for an attacker to exploit the vulnerability to run code, by significantly limiting the types of data that could be included in an URL. It would, however, still be possible to conduct denial of service attacks.
• Best practices for web site design can prevent this vulnerability from being exposed by limiting user input that can be accepted by input fields.

OWC package buffer overrun:

• For an attack to succeed, the attacker would need to have credentials to log on to the Commerce Server 2000 computer on which the OWC package installer is kept.
• Best practices suggests that unprivileged users not be allowed to interactively log onto business-critical servers. If this recommendation has been followed, unprivileged users would not have access to Commerce Server machines.

OWC package command execution:

• For an attack to succeed, the attacker would need to have credentials to log on to the Commerce Server 2000 computer on which the OWC package installer is kept.
• Best practices suggests that unprivileged users not be allowed to interactively log onto business-critical servers. If this recommendation has been followed, unprivileged users would not have access to Commerce Server machines.

New variant of the ISAPI filter buffer overrun:

• Although Commerce Server does rely on IIS for its base web services, the AuthFilter ISAPI filter is only available as part of Commerce Server. Customers using IIS are at no risk from this vulnerability.
• The URLScan tool , if deployed using the default ruleset for Commerce Server, would make it difficult if not impossible for an attacker to exploit the vulnerability to run code, by significantly limiting the types of data that could be included in a URL. It would, however, still be possible to conduct denial of service attacks.
• 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.
• While the ISAPI filter is installed by default, it is not loaded on any web site by default. It must be enabled through the Commerce Server Administration Console in the Microsoft Management Console (MMC).

Severity Rating:

Profile Service buffer overrun:

OWC package buffer overrun:

OWC package command execution:

New variant of the ISAPI filter buffer overrun:

Aggregate severity of all vulnerabilities eliminated by patch:

The above assessment is based on the types of systems affected by the vulnerability, their typical deployment patterns, and the effect that exploiting the vulnerability would have on them. The affected API in the Profile Service is not exposed to the Internet by default. The OWC package installer requires credentials for access. The AuthFilter ISAPI filter is installed but not enabled by default: administrators must choose to enable this component.

Vulnerability identifier:

• Profile service buffer overrun: CAN-2002-0620
• OWC package buffer overrun: CAN-2002-0621
• OWC package command execution: CAN-2002-0622
• New variant of the ISAPI filter buffer overrun: CAN-2002-0623

Tested Versions:

Microsoft tested Commerce Server 2000, and Commerce 2002 to assess whether they are affected by these vulnerabilities. These vulnerabilities do not affect Microsoft Site Server 3.0 or Microsoft Site Server 3.0 Commerce Edition as these products do not include the affected components.

What vulnerabilities are addressed by this patch?
This patch addresses four vulnerabilities:

• A vulnerability that could allow an attacker to run code of their choice via the Profile Service, affecting only Commerce Server 2000.
• A buffer overrun vulnerability associated with the OWC package installer that could allow an attacker to run code of their choice, affecting only Commerce Server 2000.
• A vulnerability associated with the OWC package installer that could allow an attacker to run commands of their choice, affecting only Commerce Server 2000.
• A new variant of the ISAPI Filter vulnerability discussed in Microsoft Security Bulletin MS02-010. This variant affects both Commerce Server 2000 and Commerce Server 2002.

What's Microsoft Commerce Server?
Commerce Server is a web server product that's tailored for building e-commerce sites. It provides tools and features that simplify developing and deploying e-commerce solutions, and also provides tools that let the site administrator analyze the usage of the site.

I'm running Site Server 3.0 Commerce Edition. Am I affected by these vulnerabilities?
No. Site Server 3.0 and Site Server 3.0 Commerce Edition, the predecessor product to Commerce Server 2000, are not affected by these vulnerabilities.

Profile Service buffer overrun (CVE-CAN-2002-0620)

What's the scope of the first vulnerability?
This is a buffer overrun vulnerability. An attacker who successfully exploited this vulnerability could gain complete control over an affected IIS server. This would give the attacker the ability to add, delete or change any data on the server, reformat the hard drive, or take other actions.
For an attack to succeed, the attacker would need to have credentials to log on to the Commerce Server web site, and so would either have to be a registered user or go to a Commerce Server web site that allows self-registration.
If the site is using URLscan or follows best practices with regard to limiting user input, then the risks of a successful attack against a Commerce Server site would be significantly reduced.

What causes the vulnerability? 
The vulnerability results because an API method in the Profile Service contains an unchecked buffer. The administrator setting up the Commerce Server site may choose to include the Profile Service and the affected API.

What is the Profile Service used for? 
Using the Commerce Server Profile Service, web sites can provide users with the ability to manage their own profile information. Users could research the status of orders, be presented with custom catalogs, and receive discounts and advertising tailored for them. The Profile Service also helps organizations to store and manage customer information so as to provide better service and offerings for their customers.

Is the Profile Service installed by default? 
The Profile Service is installed by default, but not enabled by default. The administrator setting up the Commerce Server site may choose to use the capabilities provided by Profile Services on the site.
For example, Commerce Server 2000 comes with three Solution Sites, which are development reference sites that provide an integrated set of features included in Commerce Server. The administrator setting up Commerce Server could use the Retail Solution Site to set up a business-to-consumer web site. This Solution Site includes the ability for users to manage their own profile information and to view their order status.

What would this vulnerability enable an attacker to do? 
Depending on the specific data the attacker chose, either of two effects could occur:

• If the data were randomly selected, the IIS process would fail.
• If the data were carefully selected, it could be possible for the attacker to run code of their choice on the Commerce Server system.

How might an attacker exploit the vulnerability? 
An attacker would first have to logon to a Commerce Server site using credentials that are valid for the site. This means they would need to either already have valid credentials or the site would have to allow users to set up credentials on their own, using self-registration that has been set up by the Commerce Server administrator. They would then have to visit a page that is using the affected Profile Service APIs. The attacker would supply specially malformed data to an input field that is using an affected Profile Service API.

Could an attack be carried out across the Internet? 
Yes, as long as the attacker had credentials on the Commerce Server, as discussed above, he could seek to exploit this vulnerability remotely across the Internet.

Could this vulnerability be exploited by accident? 
No. The attacker would have to submit specially malformed data as input to the affected Profile Service calls.

I've installed the URLScan tool on my server. Will it prevent attacks via this vulnerability? 
By default, the URLscan tool would prevent an attacker from using the vulnerability to gain control over the server. This is because the default ruleset for Commerce Server outlaws certain types of data, without which it wouldn't be possible to modify the Commerce Server process to take meaningful action. By default, only ASCII data is allowed to pass.
On the other hand, even with URLScan installed, an attacker could still cause the Commerce Server process to fail. As a result, even customers who are using URLScan should install the patch.

What does the patch do? 
The patches eliminates the vulnerability by instituting proper buffer handling within the Profile Service.

OWC package buffer overrun (CVE-CAN-2002-0621)

What's the scope of the second vulnerability?
This is a buffer overrun vulnerability. An attacker who successfully exploited this vulnerability would gain complete control over the machine. This would allow the attacker to take any desired action on the machine, such as adding, deleting, or modifying data on the system, creating or deleting user accounts, and adding accounts to the local administrators group.
For an attack to succeed, the attacker would need to have credentials to log on to the computer and access to the directory where the OWC package is held. Best practices suggests that unprivileged users not be allowed to interactively log onto business-critical servers; so if best practices were followed, systems such as a Commerce Server computer would not be at risk from this vulnerability.

What causes the vulnerability? 
The vulnerability results because the OWC Package contains an unchecked buffer.

What is the OWC Package for? 
This installer package contains the Office Web Components that are shipped for use with Commerce Server. Running this executable puts the Office Web Components onto the computer for use with Commerce Server. The Office Web Components are installed by default when you set up Commerce Server 2000.

How are Office Web Components used by Commerce Server? 
The Office Web Components are used by Commerce Server Business Desk. Commerce Server Business Desk is a Web-based site management tool included with Microsoft Commerce Server 2000. Business Desk hosts business management modules that you use to configure, manage, and analyze your Commerce Server site.

What would this enable an attacker to do? 
Depending on the specific data the attacker chose, either of two effects could occur:

• If the data were randomly selected, the IIS process would fail.
• If the data were carefully selected, it could be possible for the attacker to run code of their choice on the Commerce Server system in the LocalSystem context.

How might an attacker exploit the vulnerability? 
An attacker would need to access the Commerce Server system using log on credentials and then run the OWC package installer with specially malformed data supplied as an input parameter.

What does the patch do? 
The patch mitigates the vulnerability by changing the IIS permissions on the directory containing the OWC package installer from "script and executables" to "none". This disallows remote execution of programs from the directory.

But I thought you said this was a buffer overrun vulnerability, why doesn't the patch fix the unchecked buffer? 
There is a security investigation currently underway regarding the Office Web Components. Because of that, we felt it was not appropriate to ship a security patch that contained a component that potentially suffers from a different, unrelated security issue. On the other hand, we felt it was not appropriate for these issues to remain unaddressed while we continue that investigation.
For that reason, we felt it best to address this vulnerability with a near-term solution that mitigates the exposure to this issue. The investigation into OWC is continuing as quickly as possible and a remediation that fully addresses the unchecked buffer will be available as soon as that is completed.

If the patch mitigates the vulnerability, is there anything I can do to eliminate it entirely? 
Yes, the OWC package installer is named BDOWC.EXE and can be erased. The OWC package is only used for installation of the Office Web Components. The BDOWC.EXE program resides in the subdirectory

/Program Files/Microsoft Commerce Server/widgets/owc

and can be erased using Windows Explorer.

OWC package command execution (CVE-CAN-2002-0622)

What's the scope of the third vulnerability?
This is a vulnerability that could allow an attacker to remotely issue commands. An attacker who successfully exploited this vulnerability would be able to execute a command of their choosing via the OWC Package installer.
For an attack to succeed, the attacker would need to have credentials to log on to the computer and access to the directory where the OWC package is held. Best practices suggest that unprivileged users not be allowed to interactively log onto business-critical servers; if best practices were followed, systems such as a Commerce Server computer would not be at risk from this vulnerability.

What causes the vulnerability? 
The vulnerability results because of a feature of the OWC package installer. By design, the OWC package installer can allow a command to be passed as input. This is intended to enable administrators to be able to customize the installation of the OWC. Because of the permissions on the folder it resides in, it could actually be executed by any user who can access the Commerce Site server with valid log on credentials.

What would this enable an attacker to do? 
An attacker could use this vulnerability to execute a command on the system by passing the command as input to the OWC package installer. This could lead to running a program of the attacker's choice within the privileges associated with the attackers credentials.

What does the patch do? 
As with the second vulnerabilty described above, the patches mitigates the vulnerability by changing the IIS permissions on the directory containing the OWC package installer from "script and executables" to "none". This disallows remote execution of programs from the directory.

New variant of the ISAPI filter buffer overrun (CVE-CAN-2002-0623)

What's the scope of the fourth vulnerability?
This is a new variant of the ISAPI filter buffer overrun vulnerability discussed in MS02-010. An attacker who successfully exploited this vulnerability could gain complete control over an affected commerce web server. This would give the attacker the ability to take any desired action on the server, including changing web pages, reformatting the hard drive or adding new users to the local administrators group.
The vulnerability only affects web sites that use Microsoft Commerce Server; those using IIS are not at risk. Also, if a recommended tool has been applied to the server, the seriousness of the vulnerability would be significantly reduced. Specifically, if the URLScan tool were in use, the vulnerability could only be used to cause the service to fail, after which point it would automatically restart itself. The URLScan tool is not installed by default.

Are there any differences between this vulnerability and the one discussed in MS02-010? 
The new variant is exactly the same as the original one, except for the specific way in which it could be exploited.

Where can I get more information on the ISAPI filter vulnerability? 
Microsoft Security Bulletin MS02-010 discusses this vulnerability in detail.

What does the patch do? 
The patch eliminates the vulnerability by instituting proper buffer handling for the new variant within the AuthFilter ISAPI filter.

Download locations for this patch

• Microsoft Commerce Server 2000:

  http://www.microsoft.com/downloads/details.aspx?FamilyId=4C008857-DAF3-4E66-B74B-D56DA02AB6D6&displaylang=en

• Microsoft Commerce Server 2002:

  http://www.microsoft.com/downloads/details.aspx?FamilyId=77B05B19-BCCC-4DFA-AF41-71339435096B&displaylang=en