Microsoft Security Bulletin MS08-020 – Important Vulnerability in DNS Client Could Allow Spoofing (945553)

Microsoft Security Bulletin MS08-020 – Important
Vulnerability in DNS Client Could Allow Spoofing (945553)
Published: April 8, 2008

Version: 1.0
General Information
Executive Summary

This security update resolves a privately reported vulnerability. This spoofing vulnerability exists in Windows DNS clients and could allow an attacker to send specially crafted responses to DNS requests, thereby spoofing or redirecting Internet traffic from legitimate locations.

This is an important security update for Windows Vista and all supported editions of Microsoft Windows 2000, Windows XP, and Windows Server 2003. For more information, see the subsection, Affected and Non-Affected Software, in this section.

This security update addresses the vulnerability by increasing the randomness of DNS transaction IDs. For more information about the vulnerability, see the Frequently Asked Questions (FAQ) subsection for the specific vulnerability entry under the next section, Vulnerability Information.

Recommendation. Microsoft recommends that customers apply the update at the earliest opportunity.

Known Issues. None
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Affected and Non-Affected Software

The software listed here have been tested to determine which versions or editions are affected. Other versions or editions are either past their support life cycle or are not affected. To determine the support life cycle for your software version or edition, visit Microsoft Support Lifecycle.

Affected Software
Operating System Maximum Security Impact Aggregate Severity Rating Bulletins Replaced by This Update

Microsoft Windows 2000 Service Pack 4

Spoofing

Important

None

Windows XP Service Pack 2

Spoofing

Important

None

Windows XP Professional x64 Edition and Windows XP Professional x64 Edition Service Pack 2

Spoofing

Important

None

Windows Server 2003 Service Pack 1 and Windows Server 2003 Service Pack 2

Spoofing

Important

None

Windows Server 2003 x64 Edition and Windows Server 2003 x64 Edition Service Pack 2

Spoofing

Important

None

Windows Server 2003 with SP1 for Itanium-based Systems and Windows Server 2003 with SP2 for Itanium-based Systems

Spoofing

Important

None

Windows Vista

Spoofing

Important

None

Windows Vista x64 Edition

Spoofing

Important

None

Non-Affected Software
Operating System

Windows Vista Service Pack 1 (all editions)

Windows Server 2008 (all editions)
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Frequently Asked Questions (FAQ) Related to This Security Update

Where are the file information details?
The file information details can be found in Microsoft Knowledge Base Article 945553.

I am using an older version or edition of the software discussed in this security bulletin. What should I do?
The affected software listed in this bulletin has been tested to determine which versions or editions are affected. Other versions and editions are past their support life cycle. To determine the support life cycle for your product and version, visit Microsoft Support Lifecycle.

It should be a priority for customers who have older versions or editions of the software to migrate to supported versions to prevent potential exposure to vulnerabilities. For more information about the Windows Product Lifecycle, visit the following Microsoft Support Lifecycle. For more information about the extended security update support period for these operating system versions, visit the Microsoft Product Support Services Web site.

Customers who require custom support for older software must contact their Microsoft account team representative, their Technical Account Manager, or the appropriate Microsoft partner representative for custom support options. Customers without an Alliance, Premier, or Authorized Contract can contact their local Microsoft sales office. For contact information, visit the Microsoft Worldwide Information Web site, select the country, and then click Go to see a list of telephone numbers. When you call, ask to speak with the local Premier Support sales manager. For more information, see the Windows Operating System Product Support Lifecycle FAQ.
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Vulnerability Information

Severity Ratings and Vulnerability Identifiers
Vulnerability Severity Rating and Maximum Security Impact by Affected Software
Affected Software DNS Spoofing Attack Vulnerability – CVE-2008-0087 Aggregate Severity Rating

Microsoft Windows 2000 Service Pack 4

Important
Spoofing

Important

Windows XP Service Pack 2

Important
Spoofing

Important

Windows XP Professional x64 Edition and Windows XP Professional x64 Edition Service Pack 2

Important
Spoofing

Important

Windows Server 2003 Service Pack 1 and Windows Server 2003 Service Pack 2

Important
Spoofing

Important

Windows Server 2003 x64 Edition and Windows Server 2003 x64 Edition Service Pack 2

Important
Spoofing

Important

Windows Server 2003 with SP1 for Itanium-based Systems and Windows Server 2003 with SP2 for Itanium-based Systems

Important
Spoofing

Important

Windows Vista

Important
Spoofing

Important

Windows Vista x64 Edition

Important
Spoofing

Important
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DNS Spoofing Attack Vulnerability – CVE-2008-0087

A spoofing vulnerability exists in Windows DNS clients. The vulnerability could allow an unauthenticated attacker to send malicious responses to DNS requests made by vulnerable clients, thereby spoofing or redirecting Internet traffic from legitimate locations.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2008-0087.

Mitigating Factors for DNS Spoofing Attack Vulnerability – CVE-2008-0087

Mitigation refers to a setting, common configuration, or general best-practice, existing in a default state, that could reduce the severity of exploitation of a vulnerability.
•

Microsoft has not identified any mitigations for this vulnerability.
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Workarounds for DNS Spoofing Attack Vulnerability – CVE-2008-0087

Workaround refers to a setting or configuration change that does not correct the underlying vulnerability but would help block known attack vectors before you apply the update.
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Microsoft has not identified any workarounds for this vulnerability.
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FAQ for DNS Spoofing Attack Vulnerability – CVE-2008-0087

What is the scope of the vulnerability?
A spoofing vulnerability exists in Windows DNS Clients. An attacker who successfully exploited this vulnerability could impersonate a legitimate address.

What causes the vulnerability?
The Windows DNS Client service doesn’t provide enough entropy in its random choice of transaction values when performing DNS queries.

What might an attacker use the vulnerability to do?
An attacker who has successfully gained information about DNS client transaction IDs could use that information to send malicious responses to DNS requests.

How could an attacker exploit the vulnerability?
An attacker who successfully exploited this vulnerability could respond to a DNS query with false or misleading information, thereby redirecting Internet traffic from legitimate locations to an address of the attacker’s choice.

What is the Domain Name System (DNS)?
Domain Name System (DNS) is one of the industry-standard suite of protocols that comprise TCP/IP. DNS is implemented using two software components: the DNS server and the DNS client (or resolver). Both components are run as background service applications. Network resources are identified by numeric IP addresses, but these IP addresses are difficult for network users to remember. The DNS database contains records that map user-friendly alphanumeric names for network resources to the IP address used by those resources for communication. In this way, DNS acts as a mnemonic device, making network resources easier to remember for network users. For more information and to view logical diagrams illustrating how DNS fits with other Windows technologies, review the article How DNS Works.

Could the vulnerability be exploited over the Internet?
Yes, an attacker could exploit this vulnerability over the Internet by sending specific responses to an Internet-facing client system that is performing DNS queries.

What systems are primarily at risk from the vulnerability?
Any Windows system that is connected to the Internet or another network populated by potentially hostile users would be at risk. Windows XP Service Pack 3, Windows Vista SP1, and Windows Server 2008 are not affected by this vulnerability.

What does the update do?
The update removes this vulnerability by increasing the randomness of the transaction IDs in DNS client communications.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through responsible disclosure.

When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited?
No. Microsoft had not received any information to indicate that this vulnerability had been publicly used to attack customers and had not seen any examples of proof of concept code published when this security bulletin was originally issued.
Other Information
Acknowledgments

Microsoft thanks the following for working with us to help protect customers:
•

Amit Klein of Trusteer for reporting the DNS Spoofing Attack Vulnerability – (CVE-2008-0087).
•

Alla Berzroutchko of Scanit for reporting the DNS Spoofing Attack Vulnerability – (CVE-2008-0087).
•

Roy Arends of Nominet UK for reporting the DNS Spoofing Attack Vulnerability – (CVE-2008-0087).
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Support
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Customers in the U.S. and Canada can receive technical support from Microsoft Product Support Services at 1-866-PCSAFETY. There is no charge for support calls that are associated with security updates.
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International customers can receive support from their local Microsoft subsidiaries. There is no charge for support that is associated with security updates. For more information about how to contact Microsoft for support issues, visit the International Support Web site.

Disclaimer

The information provided in the Microsoft Knowledge Base is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.
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Revisions
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V1.0 (April 8, 2008): Bulletin published.