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Microsoft Security Bulletin MS09-042 - Important

Vulnerability in Telnet Could Allow Remote Code Execution (960859)

Published: | Updated:

Version: 1.1

General Information

Executive Summary

This security update resolves a publicly disclosed vulnerability in the Microsoft Telnet service. The vulnerability could allow an attacker to obtain credentials and then use them to log back into affected systems. The attacker would then acquire user rights on a system identical to the user rights of the logged-on user. This scenario could ultimately result in remote code execution on affected systems. An attacker who successfully exploited this vulnerability could install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.

This security update is rated Important for all supported editions of Microsoft Windows 2000, Windows XP, and Windows Server 2003, and Moderate for all supported editions of Windows Vista and Windows Server 2008. For more information, see the subsection, Affected and Non-Affected Software, in this section.

The security update addresses the vulnerability by modifying the way that the Telnet service validates authentication replies in order to prevent the relay of credentials. 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. The majority of customers have automatic updating enabled and will not need to take any action because this security update will be downloaded and installed automatically. Customers who have not enabled automatic updating need to check for updates and install this update manually. For information about specific configuration options in automatic updating, see Microsoft Knowledge Base Article 294871.

For administrators and enterprise installations, or end users who want to install this security update manually, Microsoft recommends that customers apply the update at the earliest opportunity using update management software, or by checking for updates using the Microsoft Update service.

See also the section, Detection and Deployment Tools and Guidance, later in this bulletin.

Known Issues. Microsoft Knowledge Base Article 960859 documents the currently known issues that customers may experience when installing this security update. The article also documents recommended solutions for these issues.

Affected and Non-Affected Software

The following software 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 SystemMaximum Security ImpactAggregate Severity RatingBulletins Replaced by this Update
Microsoft Windows 2000 Service Pack 4Remote Code ExecutionImportantNone
Windows XP Service Pack 2 and Windows XP Service Pack 3Remote Code ExecutionImportantNone
Windows XP Professional x64 Edition Service Pack 2Remote Code ExecutionImportantNone
Windows Server 2003 Service Pack 2Remote Code ExecutionImportantNone
Windows Server 2003 x64 Edition Service Pack 2Remote Code ExecutionImportantNone
Windows Server 2003 with SP2 for Itanium-based SystemsRemote Code ExecutionImportantNone
Windows Vista, Windows Vista Service Pack 1, and Windows Vista Service Pack 2Remote Code ExecutionModerateNone
Windows Vista x64 Edition, Windows Vista x64 Edition Service Pack 1, and Windows Vista x64 Edition Service Pack 2Remote Code ExecutionModerateNone
Windows Server 2008 for 32-bit Systems and Windows Server 2008 for 32-bit Systems Service Pack 2*Remote Code ExecutionModerateNone
Windows Server 2008 for x64-based Systems and Windows Server 2008 for x64-based Systems Service Pack 2*Remote Code ExecutionModerateNone
Windows Server 2008 for Itanium-based Systems and Windows Server 2008 for Itanium-based Systems Service Pack 2Remote Code ExecutionModerateNone

*Windows Server 2008 server core installation affected. For supported editions of Windows Server 2008, this update applies, with the same severity rating, whether or not Windows Server 2008 was installed using the Server Core installation option. For more information on this installation option, see Server Core. Note that the Server Core installation option does not apply to certain editions of Windows Server 2008; see Compare Server Core Installation Options.

Non-Affected Software

Operating System
Windows 7 for 32-bit Systems
Windows 7 for x64-based Systems
Windows Server 2008 R2 for x64-based Systems
Windows Server 2008 R2 for Itanium-based Systems

Frequently Asked Questions (FAQ) Related to This Security Update

Vulnerability Information

Severity Ratings and Vulnerability Identifiers

Telnet Credential Reflection Vulnerability - CVE-2009-1930

Update Information

Detection and Deployment Tools and Guidance

Security Update Deployment

Other Information

Microsoft Active Protections Program (MAPP)

To improve security protections for customers, Microsoft provides vulnerability information to major security software providers in advance of each monthly security update release. Security software providers can then use this vulnerability information to provide updated protections to customers via their security software or devices, such as antivirus, network-based intrusion detection systems, or host-based intrusion prevention systems. To determine whether active protections are available from security software providers, please visit the active protections Web sites provided by program partners, listed in Microsoft Active Protections Program (MAPP) Partners.

Support

  • Customers in the U.S. and Canada can receive technical support from Security Support or 1-866-PCSAFETY. There is no charge for support calls that are associated with security updates. For more information about available support options, see Microsoft Help and Support.
  • 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.

Revisions

  • V1.0 (August 11, 2009): Bulletin published.
  • V1.1 (August 12, 2009): Linked to the Knowledge Base article for known issues. Added mitigation factor for Windows Vista and Windows Server 2008. Added FAQ about different severities for Windows platforms. Corrected restart requirements. This is an informational change only. Customers who have successfully installed updates for their systems do not need to reinstall.