Microsoft Security Bulletin MS14-053 - Important

• 10/11/2017
• 39 minutes to read
• • 

Vulnerability in .NET Framework Could Allow Denial of Service (2990931)

Published: September 9, 2014 | Updated: September 17, 2014

Version: 1.1

General Information

Executive Summary

This security update resolves one privately reported vulnerability in Microsoft .NET Framework. The vulnerability could allow denial of service if an attacker sends a small number of specially crafted requests to an affected .NET-enabled website, service, or program that uses Windows Communication Foundation (WCF). By default, no WCF programs are installed when Microsoft .NET Framework is installed on any supported edition of Microsoft Windows. To be affected by the vulnerability, customers must manually install a .NET-enabled website, service, or program that uses Windows Communication Foundation (WCF).

This security update is rated Important for Microsoft .NET Framework 1.1 Service Pack 1, Microsoft .NET Framework 2.0 Service Pack 2, Microsoft .NET Framework 3.0 Service Pack 2, Microsoft .NET Framework 3.5, Microsoft .NET Framework 3.5.1, Microsoft .NET Framework 4, and Microsoft .NET Framework 4.5/4.5.1/4.5.2 on affected releases of Microsoft Windows. For more information, see the Affected and Non-Affected Software section.

The security update addresses the vulnerabilities correcting how Microsoft .NET Framework handles specially crafted requests. For more information about the vulnerabilities, see the Frequently Asked Questions (FAQ) subsection for the specific vulnerability later in this bulletin.

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. For information about specific configuration options in automatic updating, see Microsoft Knowledge Base Article 294871. For customers who do not have automatic updating enabled, the steps in Turn automatic updating on or off can be used to enable automatic updating.

For administrators and enterprise installations, or end users who want to install this security update manually (including customers who have not enabled automatic updating), 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. The updates are also available via the download links in the Affected Software table later in this bulletin.

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

Knowledge Base Article

• Knowledge Base Article: 2990931
• File Information: Yes
• SHA1/SHA2 hashes: Yes
• Known issues: None

Affected and Non-Affected Software

The following software has 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.

^[2]This update is available via Windows Update.

Non-Affected Software

.NET Framework Denial of Service Vulnerability - CVE-2014-4072

A denial of service vulnerability exists in the way that Microsoft .NET Framework handles specially crafted requests, causing a hash collision. An attacker who successfully exploited this vulnerability could send a small number of specially crafted requests to a .NET server, causing performance to degrade significantly enough to cause a denial of service condition.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2014-4072.

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:

• By default, no WCF programs are installed when Microsoft .NET Framework is installed on any supported edition of Microsoft Windows. To be affected by the vulnerability, customers must manually install a .NET-enabled website, service, or program that uses Windows Communication Foundation (WCF).

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:

• Enable UseRandomizedStringHashAlgorithm application configuration runtime setting for desktop applications
  In developing desktop applications targeting .NET 4.5 and above, you can employ the <UseRandomizedStringHashAlgorithm> element to generate unique hash codes on a per-application-domain basis. This can reduce the number of collisions and improve the overall performance of insertions and lookups that use hash tables.

  For more information see the MSDN Developer Network entry, <UseRandomizedStringHashAlgorithm> Element.

Impact of workaround. This workaround is not compatible with ASP.NET applications and is not available in versions of .NET below Microsoft .NET Framework 4.5. The workaround should not be applied in either of these environments.

FAQ

What is the scope of the vulnerability?
This is a denial of service vulnerability.****This vulnerability allows for an unauthenticated attacker to degrade the performance of a .NET-enabled website, creating a denial of service condition.

What causes the vulnerability?
The vulnerability exists when Microsoft .NET Framework hashes specially crafted requests and inserts that data into a hash table, causing a hash collision. When many of these collisions are chained together, the performance of the hash table is greatly degraded, leading to the denial of service condition.

What might an attacker use the vulnerability to do?
An attacker could use this vulnerability to cause a denial of service attack and disrupt the availability of applications that use Microsoft .NET framework.

How could an attacker exploit the vulnerability?
To exploit this vulnerability, an unauthenticated attacker could send a small number of specially crafted requests to an affected .NET-enabled website, service, or program that uses Windows Communication Foundation (WCF), causing a denial of service condition.

What systems are primarily at risk from the vulnerability?
Servers running affected versions of Microsoft .NET Framework are primarily at risk from this vulnerability.

What does the update do?
The update addresses this vulnerability by correcting how Microsoft .NET Framework handles specially crafted requests.

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.

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 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

Windows Server 2003 (all editions)

Reference Table

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

Windows Vista (all editions)

Reference Table

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

Windows Server 2008 (all editions)

Reference Table

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

Windows 7 (all editions)

Reference Table

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

Windows Server 2008 R2 (all editions)

Reference Table

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

Windows 8 and Windows 8.1 (all editions)

Reference Table

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

Windows Server 2012 and Windows Server 2012 R2 (all editions)

Reference Table

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