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Microsoft Security Advisory 3009008

  • Article

Vulnerability in SSL 3.0 Could Allow Information Disclosure

Published: October 14, 2014 | Updated: April 14, 2015

Version: 3.0

General Information

Executive Summary

Microsoft is aware of detailed information that has been published describing a new method to exploit a vulnerability in SSL 3.0. This is an industry-wide vulnerability affecting the SSL 3.0 protocol itself and is not specific to the Windows operating system. All supported versions of Microsoft Windows implement this protocol and are affected by this vulnerability. Microsoft is not aware of attacks that try to use the reported vulnerability at this time. Considering the attack scenario, this vulnerability is not considered high risk to customers.

We are actively working with partners in our Microsoft Active Protections Program (MAPP) to provide information that they can use to provide broader protections to customers.

Microsoft is announcing that with the release of security update 3038314 on April 14, 2015 SSL 3.0 is disabled by default in Internet Explorer 11. Microsoft is also announcing that SSL 3.0 will be disabled across Microsoft online services over the coming months. We recommend customers migrate clients and services to more secure security protocols, such as TLS 1.0, TLS 1.1 or TLS 1.2.

Mitigating Factors:

  • The attacker must make several hundred HTTPS requests before the attack could be successful.
  • TLS 1.0, TLS 1.1, TLS 1.2, and all cipher suites that do not use CBC mode are not affected.

Recommendation. Please see the Suggested Actions section of this advisory for workarounds to disable SSL 3.0. Microsoft recommends customers use these workarounds to test their clients and services for the usage of SSL 3.0 and start migrating accordingly.

Advisory Details

Issue References

For more information about this issue, see the following references:

References Identification
Knowledge Base Article 3009008
CVE Reference CVE-2014-3566 

Affected Software

This advisory discusses the following software.

Affected Software

|**Operating System**| |------------| |Windows Server 2003 Service Pack 2| |Windows Server 2003 x64 Edition Service Pack 2| |Windows Server 2003 with SP2 for Itanium-based Systems| |Windows Vista Service Pack 2| |Windows Vista x64 Edition Service Pack 2| |Windows Server 2008 for 32-bit Systems Service Pack 2| |Windows Server 2008 for x64-based Systems Service Pack 2| |Windows Server 2008 for Itanium-based Systems Service Pack 2| |Windows 7 for 32-bit Systems Service Pack 1| |Windows 7 for x64-based Systems Service Pack 1| |Windows Server 2008 R2 for x64-based Systems Service Pack 1| |Windows Server 2008 R2 for Itanium-based Systems Service Pack 1| |Windows 8 for 32-bit Systems| |Windows 8 for x64-based Systems| |Windows 8.1 for 32-bit Systems| |Windows 8.1 for x64-based Systems| |Windows Server 2012| |Windows Server 2012 R2| |Windows RT| |Windows RT 8.1| |**Server Core installation option**| |Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation)| |Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation)| |Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation)| |Windows Server 2012 (Server Core installation)| |Windows Server 2012 R2 (Server Core installation)|

 

Advisory FAQ


I am using a version of Internet Explorer other than 11. How can I protect my system from this vulnerability?
SSL 3.0 has only been disabled in Internet Explorer 11 on all supported editions of Microsoft Windows. If you are using a different version of Internet Explorer, please see the Suggested Workarounds section for workarounds that you can apply to your system to protect it from this vulnerability.

What is the scope of the advisory?
The purpose of this advisory is to notify customers that Microsoft is aware of detailed information describing a new method to exploit a vulnerability affecting SSL 3.0. This vulnerability is an information disclosure vulnerability.

How could an attacker exploit the vulnerability?
In a man-in-the-middle (MiTM) attack, an attacker could downgrade an encrypted TLS session forcing clients to use SSL 3.0 and then force the browser to execute malicious code. This code sends several requests to a target HTTPS website, where cookies are sent automatically if a previous authenticated session exists. This is a required condition in order to exploit this vulnerability. The attacker could then intercept this HTTPS traffic, and by exploiting a weakness in the CBC block cipher in SSL 3.0, could decrypt portions of the encrypted traffic (e.g. authentication cookies).

What might an attacker use this vulnerability to do?
An attacker who successfully exploited this vulnerability could decrypt portions of the encrypted traffic.

What causes the vulnerability?
The vulnerability is caused by the lack of CBC block cipher padding verification in SSL 3.0.

What is SSL?
Secure Sockets Layer (SSL) is a cryptographic protocol that provides communication security over the Internet. SSL encrypts the data transported over the network, using cryptography for privacy and a keyed message authentication code for message reliability.

What is TLS?
Transport Layer Security (TLS) is a standard protocol that is used to provide secure web communications on the Internet or on intranets. It enables clients to authenticate servers or, optionally, servers to authenticate clients. It also provides a secure channel by encrypting communications. TLS is the latest version of the Secure Sockets Layer (SSL) protocol.

Is TLS affected by this issue?
No. This issue is specific to SSL 3.0.

Is this an industry-wide issue?
Yes. The vulnerability resides in the design of the SSL 3.0 protocol and is not limited to Microsoft’s implementation.

Suggested Actions

Apply Workarounds

Workarounds refer to a setting or configuration change that does not correct the underlying issue but would help block known attack vectors before a security update is available.

  • Disable SSL 3.0 and enable TLS 1.0, TLS 1.1, and TLS 1.2 in Internet Explorer

    You can disable the SSL 3.0 protocol in Internet Explorer by modifying the Advanced Security settings in Internet Explorer.

    To change the default protocol version to be used for HTTPS requests, perform the following steps:

    1. On the Internet Explorer Tools menu, click InternetOptions.
    2. In the InternetOptions dialog box, click the Advanced tab.
    3. In the Security category, uncheck UseSSL3.0 and check Use TLS 1.0, Use TLS 1.1, and Use TLS 1.2 (if available).
    4. Note It is important to check consecutive versions. Not selecting consecutive versions (e.g. checking TLS 1.0 and 1.2, but not checking 1.1) could result in connection errors.
    5. Click OK.
    6. Exit and restart Internet Explorer.

    Note  After applying this workaround, Internet Explorer will fail to connect to Web servers that only support SSL up to 3.0 and don’t support TLS 1.0, TLS 1.1, and TLS 1.2. 

    Note:
    See Microsoft Knowledge Base Article 3009008 to use the automated Microsoft Fix it solution to disable SSL 3.0 in Internet Explorer only.

    How to undo the workaround. Follow these steps to enable SSL 3.0 in Internet Explorer.

    1. On the Internet Explorer Tools menu, click InternetOptions.
    2. In the InternetOptions dialog box, click the Advanced tab.
    3. In the Security category, check UseSSL3.0.
    4. Click OK.
    5. Exit and restart Internet Explorer.

  • Disable SSL 3.0 and enable TLS 1.0, TLS 1.1, and TLS 1.2 for Internet Explorer in Group Policy

    You can disable support for the SSL 3.0 protocol in Internet Explorer via Group Policy by modifying the Turn Off Encryption Support Group Policy Object.

    1. Open Group Policy Management.

    2. Select the group policy object to modify, right click and select Edit.

    3. In the Group Policy Management Editor, browse to the following setting:
      Computer Configuration -> Administrative Templates -> Windows Components -> Internet Explorer -> Internet Control Panel -> Advanced Page -> Turn off encryption support

    4. Double-click the Turn off Encryption Support setting to edit the setting.

    5. Click Enabled.

    6. In the Options window, change the Secure Protocol combinations setting to "Use TLS 1.0, TLS 1.1, and TLS 1.2".

    7. Note It is important to check consecutive versions. Not selecting consecutive versions (e.g. checking TLS 1.0 and 1.2, but not checking 1.1) could result in connection errors.

    8. Click OK.

      Note Administrators should make sure this group policy is applied appropriately by linking the GPO to the appropriate OU in their environment.

    Note After applying this workaround, Internet Explorer will fail to connect to Web servers that only support SSL up to 3.0 and don’t support TLS 1.0, TLS 1.1, and TLS 1.2. 

    How to undo the workaround. Follow these steps to disable the SSL 3.0 policy setting:

    1. Open Group Policy Management.

    2. Select the group policy object to modify, right click and select Edit.

    3. In the Group Policy Management Editor, browse to the following setting:
      Computer Configuration -> Administrative Templates -> Windows Components -> Internet Explorer -> Internet Control Panel -> Advanced Page -> Turn off encryption support

    4. Double-click the Turn off Encryption Support setting to edit the setting.

    5. Click Disabled.

    6. Click OK.

  • Disable SSL 3.0 in Windows

    For Server Software

    You can disable support for the SSL 3.0 protocol on Windows by following these steps:

    1. Click Start, click Run, type regedt32 or type regedit, and then click OK.
    2. In Registry Editor, locate the following registry key:

    HKey_Local_Machine\System\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\SSL 3.0\Server

    Note If the complete registry key path does not exist, you can create it by expanding the available keys and using the New -> Key option from the Edit menu.

    1. On the Edit menu, click AddValue.
    2. In the DataType list, click DWORD.
    3. In the ValueName box, type Enabled, and then click OK. 

    Note If this value is present, double-click the value to edit its current value.

    1. In the Edit DWORD (32-bit) Value dialog box, type 0 .
    2. Click OK. Restart the computer.

     

    Note This workaround will disable SSL 3.0 for all server software installed on a system, including IIS.

    Note After applying this workaround, clients that rely only on SSL 3.0 will not be able to communicate with the server.

    How to undo the workaround. Follow these steps to disable SSL 3.0 in Windows server software:

    1. Open Registry Editor.
    2. Locate and then click the following registry sub key:

    HKey_Local_Machine\System\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\SSL 3.0\Server

    1. On the Edit menu, click Delete.
    2. Click Yes when prompted.
    3. Exit Registry Editor.
    4. Restart the system.

    For Client Software

    You can disable support for the SSL 3.0 protocol on Windows by following these steps:

    1. Click Start, click Run, type regedt32 or type regedit, and then click OK.
    2. In Registry Editor, locate the following registry key:

    HKey_Local_Machine\System\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\SSL 3.0\Client

    Note If the complete registry key path does not exist, you can create it by expanding the available keys and using the New -> Key option from the Edit menu.

    1. On the Edit menu, click AddValue.
    2. In the DataType list, click DWORD.
    3. In the ValueName box, type Enabled, and then click OK. 

    Note If this value is present, double-click the value to edit its current value.

    1. In the Edit DWORD (32-bit) Value dialog box, type 0 .
    2. Click OK. Restart the computer.

     

    Note This workaround will disable SSL 3.0 for all client software installed on a system.

    Note After applying this workaround, client applications on this machine will not be able to communicate with other servers that only support SSL 3.0.

    How to undo the workaround. Follow these steps to disable SSL 3.0 in Windows client software:

    1. Open Registry Editor.
    2. Locate and then click the following registry sub key:

    HKey_Local_Machine\System\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\SSL 3.0\Client

    1. On the Edit menu, click Delete.
    2. Click Yes when prompted.
    3. Exit Registry Editor.
    4. Restart the system.

Additional Suggested Actions

  • Protect your PC

    We continue to encourage customers to follow our Protect Your Computer guidance of enabling a firewall, getting software updates and installing antivirus software. For more information, see Microsoft Safety & Security Center.

  • Keep Microsoft Software Updated

    Users running Microsoft software should apply the latest Microsoft security updates to help make sure that their computers are as protected as possible. If you are not sure whether your software is up to date, visit Microsoft Update, scan your computer for available updates, and install any high-priority updates that are offered to you. If you have automatic updating enabled and configured to provide updates for Microsoft products, the updates are delivered to you when they are released, but you should verify that they are installed.

Acknowledgments

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

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 websites provided by program partners, listed in Microsoft Active Protections Program (MAPP) Partners.

Feedback

Support

Disclaimer

The information provided in this advisory 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 (October 14, 2014): Advisory published.
  • V1.1 (October 15, 2014): Revised advisory to include a workaround for disabling the SSL 3.0 protocol in Windows.
  • V2.0 (October 29, 2014): Revised advisory to announce the deprecation of SSL 3.0, to clarify the workaround instructions for disabling SSL 3.0 on Windows servers and on Windows clients, and to announce the availability of a Microsoft Fix it solution for Internet Explorer. For more information see Knowledge Base Article 3009008.
  • V2.1 (December 9, 2014): Microsoft is announcing the availability of SSL 3.0 fallback warnings in Internet Explorer 11. For more information see Knowledge Base Article 3013210.
  • V2.2 (February 10, 2015): Microsoft is announcing that SSL 3.0 fallback attempts are disabled by default in Internet Explorer 11. For more information see Microsoft Knowledge Base Article 3021952.
  • V2.3 (February 16, 2015): Revised advisory to announce the planned date for disabling SSL 3.0 by default in Internet Explorer 11.
  • V3.0 (April 14, 2015) Revised advisory to announce with the release of security update 3038314 on April 14, 2015 SSL 3.0 is disabled by default in Internet Explorer 11, and to add instructions for how to undo the workarounds.

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