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Microsoft Rolls Out Spectre Variant 2 Mitigations for Windows 10

Over the weekend, Microsoft started rolling out a new software update for Windows 10 devices to enable the Retpoline mitigations against Spectre attacks. 

Over the weekend, Microsoft started rolling out a new software update for Windows 10 devices to enable the Retpoline mitigations against Spectre attacks. 

Publicly detailed in January 2018 along with Meltdown, Spectre is a side-channel attack against modern processors that impacts most modern processors, including those from Intel, AMD, and ARM.

Able to bypass memory isolation mechanisms, the attacks allow malicious applications to access data from other applications, including password managers, web browser, documents, emails, instant messaging data, and more. 

Multiple variants of these attacks were made public over the course of last year (Spectre Variant 1 – CVE-2017-5753 and Variant 2 – CVE-2017-5715 and Meltdown Variant 3 – CVE-2017-5754), and Microsoft released patches for some of these too, including Spectre-like variant 4

Over the weekend, the company started rolling out new updates for Windows 10 users to enable Google’s Retpoline mitigations for Spectre Variant 2. 

Available since early 2018, the Retpoline mitigations were already included in Windows 10, but disabled by default on production builds. The update Microsoft released over the weekend enables the mitigation, on certain devices, which “may improve performance of Spectre variant 2 mitigations”

“While Retpoline is currently disabled by default on production Windows 10 client devices, we have backported the OS modifications needed to support Retpoline so that it can be used with Windows 10, version 1809 and have those modifications in the March 1, 2019 update (KB4482887),” Microsoft explains.

The software giant also says it plans to enable Retpoline as part of phased rollout via cloud configuration over the next months. 

However, the company is enabling Retpoline performance benefits only in Windows 10, version 1809 and later releases, “due to the complexity of the implementation and changes involved.”

The new mitigations are enabled in OS Build 17763.348, which is available for both Windows 10, version 1809, and Windows Server 2019, all versions, and which brings other fixes and improvements as well. 

Related: Microsoft Releases Mitigations for Spectre-Like ‘Variant 4’ Attack

Related: More Chrome OS Devices Receive Meltdown, Spectre Patches

Written By

Ionut Arghire is an international correspondent for SecurityWeek.

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