Security Bulletin

Microsoft Security Bulletin MS13-095 - Important

Published: November 12, 2013 | Updated: February 28, 2014

Version: 1.1

This security update resolves a privately reported vulnerability in Microsoft Windows. The vulnerability could allow denial of service when an affected web service processes a specially crafted X.509 certificate.

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

The security update addresses the vulnerability by correcting how specially crafted X.509 certificates are handled in Microsoft Windows. 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.

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.

Affected Software 

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

Does this update contain any security related changes to functionality?
Yes. Security update 2868626 includes the functionality introduced in Microsoft Security Advisory 2661254. This functionality restricts the use of certificates with RSA keys less than 1024 bits in length.

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 has 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.

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 November bulletin summary. For more information, see Microsoft Exploitability Index.

A denial of service vulnerability exists in implementations of X.509 certificate parsing that could cause an affected web service to stop responding. The vulnerability is caused when the X.509 certificate validation operation fails to handle a specially crafted X.509 certificate.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2013-3869.

Microsoft has not identified any mitigations for this vulnerability.

Microsoft has not identified any workarounds for this vulnerability.

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

What causes the vulnerability?
The vulnerability is caused when the X.509 certificate validation operation fails to properly handle a specially crafted X.509 certificate.

What is the X.509 standard?
The X.509 specification defines a standard for managing public keys through a Public Key Infrastructure (PKI). Public keys are maintained in X.509 certificates, which are digital documents that bind a subject's identity claims to a public key from a public/private asymmetric key pair. Identity claims are usually understandable by humans, such as a person's full name or email address, or a machine host name or domain name. X.509 certificates are endorsed and issued by a trusted third party, which is known as a certificate authority (CA).

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could cause an affected web service to become non-responsive.

How could an attacker exploit the vulnerability?
An attacker could exploit this vulnerability by sending a specially crafted X.509 certificate to a web service. The web service could become non-responsive when it performs certificate validation.

What systems are primarily at risk from the vulnerability?
Servers are primarily at risk.

What does the update do?
The update addresses the vulnerability by correcting how specially crafted X.509 certificates are handled in Microsoft Windows.

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.

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. 

Affected Software

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

Reference Table

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

Note The update for supported versions of Windows XP Professional x64 Edition also applies to supported versions of Windows Server 2003 x64 Edition.

Reference Table

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

Note The update for supported versions of Windows Server 2003 x64 Edition also applies to supported versions of Windows XP Professional x64 Edition.

Reference Table

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

Reference Table

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

Reference Table

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

Reference Table

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

Reference Table

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

Reference Table

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

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

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

• James Forshaw of Context Information Security for reporting the Digital Signatures Vulnerability (CVE-2013-3869)

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.

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

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.

• V1.0 (November 12, 2013): Bulletin published.
• V1.1 (February 28, 2014): Bulletin revised to announce a detection change in the 2868626 update for Windows 8.1 for 32-bit Systems, Windows 8.1 for x64-based Systems, Windows RT 8.1, and Windows Server 2012 R2. This is a detection change only. There were no changes to the update files. Customers who have already successfully updated their systems do not need to take any action.

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