Security Bulletin

Microsoft Security Bulletin MS13-039 - Important

Vulnerability in HTTP.sys Could Allow Denial of Service (2829254)

Published: May 14, 2013 | Updated: December 16, 2013

Version: 1.1

General Information

Executive Summary

This security update resolves a privately reported vulnerability in Microsoft Windows. The vulnerability could allow denial of service if an attacker sends a specially crafted HTTP packet to an affected Windows server or client.

This security update is rated Important for supported editions of Windows 8 and Windows Server 2012 For more information, see the subsection, Affected and Non-Affected Software, in this section.

The security update addresses the vulnerability by correcting the way that HTTP.sys handles certain HTTP headers. 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. Most 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.

Knowledge Base Article

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, see Microsoft Support Lifecycle.

Affected Software 

^[1]This update is available via Windows Update.

Non-Affected Software

Update FAQ

I am using an older release of the software discussed in this security bulletin. What should I do?
The affected software listed in this bulletin have been tested to determine which releases are affected. Other releases are past their support life cycle. For more information about the product lifecycle, see the Microsoft Support Lifecycle website.

It should be a priority for customers who have older releases of the software to migrate to supported releases to prevent potential exposure to vulnerabilities. To determine the support lifecycle for your software release, see Select a Product for Lifecycle Information. For more information about service packs for these software releases, see Service Pack Lifecycle Support Policy.

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, see the Microsoft Worldwide Information website, select the country in the Contact Information list, 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 Microsoft Support Lifecycle Policy FAQ.

Vulnerability Information

Severity Ratings and Vulnerability Identifiers

The following severity ratings assume the potential maximum impact of the vulnerability. For information regarding the likelihood, within 30 days of this security bulletin's release, of the exploitability of the vulnerability in relation to its severity rating and security impact, please see the Exploitability Index in the May bulletin summary. For more information, see Microsoft Exploitability Index.

HTTP.sys Denial of Service Vulnerability - CVE-2013-1305

A denial of service vulnerability exists in Windows Server 2012 and Windows 8 when the HTTP protocol stack (HTTP.sys) improperly handles a malicious HTTP header. An attacker who successfully exploited this vulnerability could trigger an infinite loop in the HTTP protocol stack by sending a specially crafted HTTP header to an affected Windows server or client.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2013-1305.

Mitigating Factors

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. The following mitigating factors may be helpful in your situation:

• Firewall best practices and standard default firewall configurations can help protect networks from attacks that originate outside the enterprise perimeter. Best practices recommend that systems connected directly to the Internet have a minimal number of ports exposed.

Workarounds

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. Microsoft has tested the following workarounds and states in the discussion whether a workaround reduces functionality:

• Block TCP ports 80 and 443 at the enterprise perimeter firewall

  TCP ports 80 and 443 are used to initiate a connection with the affected component. Blocking TCP ports 80 and 443 at the network perimeter firewall will help protect systems that are behind that firewall from attempts to exploit this vulnerability. This can help protect networks from attacks that originate outside the enterprise perimeter. Blocking the affected ports at the enterprise perimeter is the best defense to help avoid Internet-based attacks. However, systems could still be vulnerable to attacks from within their enterprise perimeter.

  Impact of workaround. HTTP and HTTPS applications will not be accessible from the external network.

  How to undo the workaround. Unblock TCP ports 80 and 443 at the enterprise perimeter firewall For more information about ports, see the TechNet article, TCP and UDP Port Assignments.

FAQ

What is the scope of the vulnerability?
This is a remote denial of service vulnerability.

What causes the vulnerability?
The vulnerability is caused when the HTTP protocol stack (HTTP.sys) improperly handles a malicious HTTP header.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability cause a system to stop responding.

How could an attacker exploit the vulnerability?
In an HTTP attack scenario, an attacker could send a specially crafted HTTP packet to an affected system and trigger the vulnerability.

What systems are primarily at risk from the vulnerability?
Systems running Windows Server 2012 in an internet-facing deployment are primarily vulnerable.

What does the update do?
The update addresses the vulnerability by correcting the way that HTTP.sys handles certain HTTP headers.

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

Update Information

Detection and Deployment Tools and Guidance

Several resources are available to help administrators deploy security updates. 

• Microsoft Baseline Security Analyzer (MBSA) lets administrators scan local and remote systems for missing security updates and common security misconfigurations. 
• Windows Server Update Services (WSUS), Systems Management Server (SMS), and System Center Configuration Manager (SCCM) help administrators distribute security updates. 
• The Update Compatibility Evaluator components included with Application Compatibility Toolkit aid in streamlining the testing and validation of Windows updates against installed applications. 

For information about these and other tools that are available, see Security Tools for IT Pros. 

Security Update Deployment

Affected Software

For information about the specific security update for your affected software, click the appropriate link:

Windows 8 (all editions)

Reference Table

The following table contains the security update information for this software.

Windows Server 2012 (all editions)

Reference Table

The following table contains the security update information for this software.

Windows RT (all editions)

The following table contains the security update information for this software.

Other Information

Acknowledgments

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

• Marek Kroemeke, 22733db72ab3ed94b5f8a1ffcde850251fe6f466, AKAT-1, working with HP's Zero Day Initiative, for reporting the HTTP.sys Denial of Service Vulnerability (CVE-2013-1305)

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 go to the active protections websites provided by program partners, listed in Microsoft Active Protections Program (MAPP) Partners.

Support

How to obtain help and support for this security update

• Help installing updates: Support for Microsoft Update
• Security solutions for IT professionals: TechNet Security Troubleshooting and Support
• Help protect your computer that is running Windows from viruses and malware: Virus Solution and Security Center
• Local support according to your country: International Support

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 (May 14, 2013): Bulletin published.
• V1.1 (December 16, 2013): Revised bulletin to announce a detection change to correct an offering issue for Windows RT (2829254). This is a detection change only. There were no changes to the update files. Customers who have successfully installed the update do not need to take any action.

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