Microsoft Security Bulletin MS14-006 - Important

Vulnerability in IPv6 Could Allow Denial of Service (2904659)

Published: February 11, 2014

Version: 1.0

General Information

Executive Summary

This security update resolves a publicly disclosed vulnerability in Microsoft Windows. The vulnerability could allow denial of service if an attacker sends a large number of specially crafted IPv6 packets to an affected system. To exploit the vulnerability, an attacker's system must belong to the same subnet as the target system.

This security update is rated Important for all supported editions of Windows 8, Windows RT, 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 modifying the way that the affected operating systems validate TCP/IP requests. 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

• Knowledge Base Article: 2904659
• 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.

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 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 , 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.

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

TCP/IP Version 6 (IPv6) Denial of Service Vulnerability - CVE-2014-0254

A denial of service vulnerability exists in Windows in the IPv6 implementation of TCP/IP. An attacker who successfully exploited this vulnerability could cause the affected system to stop responding.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2014-0254.

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:

• An attacker's system must belong to the same subnet as the target system.
• 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 that are connected to the Internet have a minimal number of ports exposed. Affected systems that allow any IP connections to the Internet may be vulnerable to this issue.

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:

• Disable the Router Discovery Protocol

  If the Router Discovery Protocol is enabled, use the following workaround to disable it. This will help prevent attempts to exploit the TCP/IP Version 6 (IPv6) Denial of Service Vulnerability.

  Run the following command from an elevated command prompt:

      netsh interface ipv6 set interface "InterfaceName" routerdiscovery=disabled
  

  Impact of workaround. Router discovery will be disabled.

  How to undo the workaround. 

  Run the following command from an elevated command prompt:

  netsh interface ipv6 set interface "InterfaceName" routerdiscovery=enabled
  

• Disable Internet Protocol version 6 (IPv6)

  You can disable IPv6 on the host through the DisabledComponents registry value. The DisabledComponents registry value affects all network interfaces on the host. For more information about disabling IPv6 components, see How to disable IP version 6 or its specific components in Windows.

  Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

  To disable certain IPv6 components yourself, follow these steps:

  1. Click Start, type regedit, and then select the regedit app.
  2. In the User Account Control dialog box, click Yes.
  3. In Registry Editor, locate and then click the following registry subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters\
  4. Double-click DisabledComponents to change the DisabledComponents entry. 

  Note If the DisabledComponents entry is unavailable, you must create it. To do this, follow these steps:

  1. In the Edit menu, point to New, and then click DWORD (32-bit) Value.
  2. Type DisabledComponents, and then press ENTER.
  3. Double-click DisabledComponents.
  4. To disable all IPv6 interfaces except for the IPv6 loopback interface, type 0x11.

  How to undo the workaround.

  1. Click Start, type regedit, and then select the regedit app.
  2. In the User Account Control dialog box, click Yes.
  3. In Registry Editor, locate and then click the following registry subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters\
  4. Double-click DisabledComponents to change the DisabledComponents entry.
  5. Type 0 to enable all IPv6 components.

   

• Disable the "Core Networking - Router Advertisement (ICMPv6-In)" inbound firewall rule

  To disable this firewall rule, run the following command from an elevated command prompt:

  netsh advfirewall firewall set rule name="Core Networking - Router Advertisement (ICMPv6-In)" dir=in new enable=No
  

  Impact of workaround. ICMPv6 router advertisements will be blocked. This could adversely impact IPv6 functionality in common deployment scenarios, where router discovery protocol is used for host configuration.

  How to undo the workaround.

  To re-enable this firewall rule, run the following command from an elevated command prompt:

  netsh advfirewall firewall set rule name="Core Networking - Router Advertisement (ICMPv6-In)" dir=in new enable=Yes
  

FAQ

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

What causes the vulnerability?
The affected operating systems perform incomplete validation of TCP/IP network packets. The vulnerability is caused when an attacker sends large amounts of specially crafted IPv6 router advertisement packets over a targeted subnet. This attack can cause denial of service on any machines belonging to the same subnet.

What is IPv6?
Internet Protocol version 6 (IPv6) is a suite of standard protocols for the network layer of the Internet that replaces IP version 4 (IPv4). IPv6 is built into Microsoft Windows XP and later. IPv6 is designed to solve many of the problems of the IPv4 such as address depletion, security, autoconfiguration, and extensibility. To learn more about IPv6, see IPv6 for Microsoft: Frequently Asked Questions.

What is TCP/IP?
TCP/IP is a set of networking protocols that are widely used on the Internet. TCP/IP provides communications across interconnected networks of computers that have diverse hardware architectures and that run various operating systems. TCP/IP includes standards for how computers communicate and conventions for connecting networks and for routing traffic. For more information about TCP/IP, see the TechNet article, Overview of networking and TCP/IP.

What are Router Advertisements?
Router Advertisements allow routers to instruct hosts how to perform address autoconfiguration. For example, routers can specify whether hosts should use DHCPv6 and/or autonomous (stateless) address configuration. Routers advertise their presence together with various link and Internet parameters either periodically, or in response to a router solicitation message. Router Advertisements contain prefixes that are used for determining whether another address shares the same link (on-link determination) and/or address configuration, a suggested hop limit value, etc. For more information about Router Advertisements and Neighbor Discovery in IPv6, see RFC 4861.

What might an attacker use the vulnerability to do?
An attacker who exploited this vulnerability could cause affected systems to stop responding.

How could an attacker exploit the vulnerability?
An attacker could exploit the vulnerability by creating a large number of specially crafted IPv6 packets and sending the packets to affected systems over a subnet network. The packets could then cause the affected systems to stop responding.

What systems are primarily at risk from the vulnerability?
All affected operating systems are at risk from this vulnerability.

What does the update do?
The update removes the vulnerability by modifying the way that the affected operating systems validate TCP/IP requests.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
Yes. This vulnerability has been publicly disclosed. It has been assigned Common Vulnerability and Exposure number CVE-2014-0254.

When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited?
No. Microsoft had seen examples of proof of concept code published publicly but had not received any information to indicate that this vulnerability had been publicly used to attack customers using IPv6 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

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)

Reference Table

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

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

Support

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 (February 11, 2014): Bulletin published.

Page generated 2014-06-25 13:31Z-07:00.