Summary
This article will be updated as additional information becomes available. Please check back here regularly for updates and new FAQs.
Microsoft is aware of a new publicly disclosed class of vulnerabilities that are called “speculative execution side-channel attacks” and that affect many modern processors including Intel, AMD, and ARM.
Note This issue also affects other operating systems, such as Android, Chrome, iOS, and macOS. Therefore, we advise customers to seek guidance from those vendors.
Microsoft has released several updates to help mitigate these vulnerabilities. We have also taken action to secure our cloud services. See the following sections for more details.
Microsoft has not yet received any information to indicate that these vulnerabilities have been used to attack customers. Microsoft is working closely with industry partners including chip makers, hardware OEMs, and app vendors to protect customers. To get all available protections, firmware (microcode) and software updates are required. This includes microcode from device OEMs and, in some cases, updates to antivirus software.
This article addresses the following vulnerabilities:
- CVE-2017-5715 – "Branch Target Injection"
- CVE-2017-5753 – "Bounds Check Bypass"
- CVE-2017-5754 – "Rogue Data Cache Load"
- CVE-2018-3639 – "Speculative Store Bypass"
To learn more about this class of vulnerabilities, see ADV180002 and ADV180012.
Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.
Recommended actions
Customers should take the following actions to help protect against the vulnerabilities:
- Apply all available Windows operating system updates, including the monthly Windows security updates. For details about how to enable these updates, see Microsoft Knowledge Base article 4072699.
- Apply applicable firmware (microcode) updates from the device manufacturer (OEM).
- Evaluate the risk to your environment based on the information that's in Microsoft Security Advisories ADV180002 and ADV180012 and in this Knowledge Base article.
- Take action as required by using the advisories and registry key information that is provided in this Knowledge Base article.
Mitigation Settings for Windows Server
Security advisories ADV180002 and ADV180012 provide information on the risk posed by these vulnerabilities and identify the default state of mitigations for Windows Server systems. The below table summarizes the requirement of CPU microcode and the default status of the mitigations on Windows Server.
CVE | Requires CPU microcode/firmware? | Mitigation Default status |
---|---|---|
CVE-2017-5753 | No | Enabled by default (no option to disable) |
CVE-2017-5715 | Yes | Disabled by default. |
CVE-2017-5754 | No | Windows Server 2019: Enabled by default. |
CVE-2018-3639 | Intel: Yes AMD: No | Disabled by default. See ADV180012 for more information and this KB article for applicable registry key settings. |
Customers who want to obtain all available protections against these vulnerabilities must make registry key changes to enable these mitigations that are disabled by default.
Enabling these mitigations may affect performance. The scale of the performance effects depends on multiple factors, such as the specific chipset in your physical host and the workloads that are running. We recommend that customers assess the performance effects for their environment and make any necessary adjustments.
Your server is at increased risk if it's in one of the following categories:
- Hyper-V hosts – Requires protection for VM-to-VM and VM-to-host attacks.
- Remote Desktop Services Hosts (RDSH) – Requires protection from one session to another session or from session-to-host attacks.
- Physical hosts or virtual machines that are running untrusted code, such as containers or untrusted extensions for database, untrusted web content, or workloads that run code that's from external sources. These require protection from untrusted process-to-another-process or untrusted-process-to-kernel attacks.
Use the following registry key settings to enable the mitigations on the server, and restart the system for the changes to take effect.
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in Windows
Manage mitigations for CVE-2017-5715 (Spectre Variant 2) and CVE-2017-5754 (Meltdown)
To enable mitigations for CVE-2017-5715 (Spectre Variant 2) and CVE-2017-5754 (Meltdown)
If this is a Hyper-V host and the firmware updates have been applied: Fully shut down all Virtual Machines. This enables the firmware-related mitigation to be applied on the host before the VMs are started. Therefore, the VMs are also updated when they're restarted. Restart the computer for the changes to take effect. To disable mitigations for CVE-2017-5715 (Spectre Variant 2) and CVE-2017-5754 (Meltdown)
Restart the computer for the changes to take effect. |
Note Setting FeatureSettingsOverrideMask to 3 is accurate for both the "enable" and "disable" settings. (See the "FAQ" section for more details about registry keys.)
Manage the mitigation for CVE-2017-5715 (Spectre Variant 2)
To disable Variant 2: (CVE-2017-5715 "Branch Target Injection") mitigation:
Restart the computer for the changes to take effect. To enable Variant 2: (CVE-2017-5715 "Branch Target Injection") mitigation:
Restart the computer for the changes to take effect. |
AMD processors only: Enable the full mitigation for CVE-2017-5715 (Spectre Variant 2)
By default, user-to-kernel protection for CVE-2017-5715 is disabled for AMD CPUs. Customers must enable the mitigation to receive additional protections for CVE-2017-5715. For more information, see FAQ #15 in ADV180002.
Enable user-to-kernel protection on AMD processors along with other protections for CVE 2017-5715:
If this is a Hyper-V host and the firmware updates have been applied: Fully shut down all Virtual Machines. This enables the firmware-related mitigation to be applied on the host before the VMs are started. Therefore, the VMs are also updated when they're restarted. Restart the computer for the changes to take effect. |
Manage mitigations for CVE-2018-3639 (Speculative Store Bypass), CVE-2017-5715 (Spectre Variant 2), and CVE-2017-5754 (Meltdown)
To enable mitigations for CVE-2018-3639 (Speculative Store Bypass), CVE-2017-5715 (Spectre Variant 2), and CVE-2017-5754 (Meltdown):
If this is a Hyper-V host and the firmware updates have been applied: Fully shut down all Virtual Machines. This enables the firmware-related mitigation to be applied on the host before the VMs are started. Therefore, the VMs are also updated when they're restarted. Restart the computer for the changes to take effect. To disable mitigations for CVE-2018-3639 (Speculative Store Bypass) AND mitigations for CVE-2017-5715 (Spectre Variant 2) and CVE-2017-5754 (Meltdown)
|
AMD processors only: Enable the full mitigation for CVE-2017-5715 (Spectre Variant 2) and CVE 2018-3639 (Speculative Store Bypass)
By default, user-to-kernel protection for CVE-2017-5715 is disabled for AMD processors. Customers must enable the mitigation to receive additional protections for CVE-2017-5715. For more information, see FAQ #15 in ADV180002.
Enable user-to-kernel protection on AMD processors along with other protections for CVE 2017-5715 and protections for CVE-2018-3639 (Speculative Store Bypass):
If this is a Hyper-V host and the firmware updates have been applied: Fully shut down all Virtual Machines. This enables the firmware-related mitigation to be applied on the host before the VMs are started. Therefore, the VMs are also updated when they're restarted. Restart the computer for the changes to take effect. |
Verifying that protections are enabled
To help customers verify that protections are enabled, Microsoft has published a PowerShell script that customers can run on their systems. Install and run the script by running the following commands.
PowerShell verification by using the PowerShell Gallery (Windows Server 2016 or WMF 5.0/5.1) |
Install the PowerShell Module:
Run the PowerShell module to verify that protections are enabled:
|
PowerShell verification by using a download from Technet (Earlier operating system versions and Earlier WMF versions) |
Install the PowerShell module from Technet ScriptCenter:
Run the PowerShell module to verify that protections are enabled: Start PowerShell, and then use the previous example to copy and run the following commands:
|
For a detailed explanation of the output of the PowerShell script, see Knowledge Base article 4074629.