Ways to Mitigate the Meltdown & Spectre Problem

To mitigate the flaws of the two large vulnerabilities vendors have been scrabbling to come out with updates to provide consumers with a fix.

If exploited, these vulnerabilities can give hackers unprecedented access to compromised systems and widespread liberty to steal a broad variety of confidential, sensitive data. Their severity, complexity and scope puts them among the most dangerous ever.

Namely, the vulnerabilities affect virtually all processors made by all big chip makers (Intel, AMD, Apple, etc.) dating back to 1995.

No Easy Fix as all of it is “Work in Progress”

There is a lot of confusion and compatibility issues that have been reported with the fixes that are coming out and vendors seem to be having a hard time working them out which is causing frustrations to a lot of consumers. I am listing the steps I have taken to mitigate the vulnerabilities.

The updates have been broken down by:

  • OS
    • Windows
    • macOS
    • Linux
  • Browser
  • Firmware
  • Cloud Platforms

Meltdown and Spectre Overview

Meltdown (rogue data cache load — CVE-2017-5754)

Meltdown is a CPU vulnerability that allows a user mode program to access privileged kernel-mode memory. It affects all out-of-order Intel processors released since 1995 with the exception of Itanium and pre-2013 Atoms. A list of vulnerable ARM processors and mitigations is listed here. No AMD processors are affected by Meltdown.

Of the two bugs, Meltdown is the easier one to fix, and can largely be addressed with operating system updates.

Spectre variant 1 (bounds check bypass — CVE-2017-5753) &Spectre variant 2 (branch target injection CVE-2017-5715)

Spectre isn’t so much a specific vulnerability as it’s a new class of attack. It’s enabled by the unintended side effects of speculative execution (something processors do to speed things up by predicting what instructions they’re about to recieve and executing them ahead of time).

There are two flavors of Spectre — variant 1 (bounds check bypass, CVE-2017-5753) and variant 2 (branch target injection, CVE-2017-5715). Both can potentially allow attackers to extract information from other running processes (ex: stealing login cookies from browsers).

Intel, ARM, and AMD processors are all reportedly affected by Spectre to some degree, and it poses significant patching problems. While operating system and browser updates have helped mitigate the risk of Spectre to some degree, experts agree the only true fix is a hardware update. As such, Spectre is likely to remain an issue for years to come.

Source: SANS / Rendition Infosec. See the full presentation here

It’s important to note that both vulnerabilities put information disclosure at risk. Neither are remote execution vulnerabilities — in other words, they don’t allow attackers to run malware.



Microsoft’s process for releasing Windows updates addressing Meltdown and Spectre has been a bumpy road, marred by high-profile incompatibility issues with third-party antivirus (AV) software and AMD processors. In some cases, delivery of the latest security update has been restricted or suspended.

More details and direct download links to the updates below:

  • Windows Server 2000, 2003 & Windows XP, Vista
    • Large enterprises may still be using systems that are over a decade old and they are still working! That said, there has been no official word from Microsoft on providing any security updates to older OS(s), because all of them have crossed their support lifecycle and are vulnerable.
    • Looking at industry trends looks like vendors are only going back 5 years for hardware microcode update and not supporting older generations processors.
    • Considering Microsoft did put out a security patch for Windows 2003 for WannaCry, it would be very surprising if they did not release a security update if there is an active exploit in the wild.

Microsoft has added capabilities to its free Windows Analytics service to help IT pros better track and manage their Meltdown and Spectre patching process. The new features include a dashboard that highlights the status of antivirus compatibility, Windows security updates, and firmware updates — all in one place for every Windows device you manage.


What the Windows updates address:

  • Spectre variant 1, bounds check bypass (CVE-2017-5753)
  • Meltdown, rogue data cache load (CVE-2017-5754)Windows patches for 32-bit systems (x86-based systems) do not provide Meltdown mitigations.
    Per Microsoft:
The existing 32 bit update packages listed in this advisory fully address CVE-2017-5753 and CVE-2017-5715, but do not provide protections for CVE-2017-5754 at this time. Microsoft is continuing to work with affected chip manufacturers and investigate the best way to provide mitigations for x86 customers, which may be provided in a future update.

What they don’t address:

Known issues:

This has created a lot of confusion, especially since the response from AV vendors has varied, with some setting the registry key for their customers and others recommending users set it, themselves, manually. The situation only gets more complicated considering many organizations have more than one AV solution installed.

Update: Microsoft has clarified that Windows Defender Antivirus, System Center Endpoint Protection, and Microsoft Security Essentials are compatible with the update and do set the required registry key.

That means as long as you have one of these built-in Microsoft protections enabled the registry key should be set automatically — no further, manual action should be necessary.

Big caveat: If you are using third party software that Microsoft offically recognizes as AV, it is important to note that, by default, Windows Defender and Microsoft Security Essentials will turn themselves off. That means the registry key won’t be added unless you or your AV actively do it.

If you are unsure, set the registry keys. You will at least be current on all Windows Updates. Even if you have an AV Provider you are just duplicating the effect.  Not fully protected until the microcode/firmware update from the chip provider is applied, but you are half way there.

All that said, here is a flow chart that can help you determine your situation:

Windows users who aren’t using a third party antivirus and don’t have Windows Defender or Microsoft Security Essentials enabled will need to set the registry key themselves, manually. To help, Bleeping Computer has put together a .reg file that automates that task here. Note: They also issue a warning to make absolutely sure you’re not running an AV that isn’t compatible with the update before using it.

If you are using an AV and haven’t received the Windows patch yet, you are advised to wait until your AV vendor either issues an update that sets the registry key for you or specifically recommends that you do so, yourself.

  • AMD compatibility issues: As first reported at the Verge, Microsoft has received numerous reports of PCs running AMD processors not booting after installing the latest Windows security update. After investigating, the company confirmed there were issues, and temporarily stopped delivering the update to AMD devices. Affected users needed to visit Microsoft’s support site for instructions on getting their machines back up and running.Update (1/18/18): Microsoft has announced it will resume rolling out patches for AMD devices running Windows 7 SP1 and Windows Server 2008 R2 SP1, Windows 8.1 and Windows Server 2012 R2, and Windows 10, version 1709. Updates for four versions of Windows 10 — 1511, 1607, and 1703 — are still paused. As are updates for Windows Server 2016 and Windows 10 Enterprise.
  • Group or MDM policy configuations may be disabling updates: According to Microsoft, if you have Group or MDM policy settings configured to disable preview builds, your machines may not be receiving updates (see what those settings are here). To fix that, Microsoft recommends temporarily changing Group/MDM policy settings to “Not Configured” and changing them back once the updates have been installed.
  • Performance impact: As with the other operating systems, patches addressing Meltdown and Spectre are expected to take a non-insignificant toll. In a blog post, Microsoft Executive VP Terry Myerson explains the impact of these fixes can vary depending on the version of Windows running and the age of the machine:
    • Windows 10 on 2016-era PCs with Skylake, Kabylake, or newer CPU: Single-digit slowdowns, which most users won’t notice.
    • Windows 10 on 2015-era PCs with Haswell or older CPU: Slowdown can be more significant. Some users may notice a decrease in performance.
    • Windows 8 or Windows 7 on 2015-era PCs with Haswell or older CPU: Most users will likely notice a decrease in system performance.
    • Windows Server (any CPU): Mitigations to isolate code within a Windows Server intance results in a more significant performance impact. According to Myerson, “This is why you want to be careful to evaluate the risk of untrusted code for each Windows Server instance, and balance the security versus performance tradeoff for your environment.”

Enabling protections for Windows Server

Microsoft has also advised Windows Server customers that they need to take the additional step of adding the following registry keys in order to enable patch protections.

Keep  in mind that the above registry key is also required.

To enable the fix:

To disable this fix:

Microsoft also notes that for Hyper-V hosts, live migration between patched and unpatched hosts may fail. The company also points to an alternative protection mechanism you can use on hosts that don’t have updated firmware yet.

Additional guidance from Microsoft:

Verifying new Windows protections are enabled:

To help confirm whether updates have been implemented correctly Microsoft has provided a PowerShell script that system administrators can run to test Meltdown and Spectre mitigations.

The following command will install the PowerShell module:

Note: There are a couple of requirements for running this command. First, you’ll need to be running PowerShell with admin privileges and may need to adjust execution policy. Also, the Install-Module command was introduced to PowerShell in version 5.0. Most Windows 7 machines will not have this version, due to the upgrades being optional and unrelated to security. Any machine with an outdated version of PowerShell can still run the Get-SpeculationControlSettings function below, however, as long as you can obtain the contents of the script and run it ad-hoc.

Once installed, the following command will run the test to check your system:

The output will look something like this:

Results for Spectre protections

The first grouping — “Speculation control settings for CVE-2017-5715 [branch target injection] — refer to protections in place for the Spectre vulneralbility. If the value for “Windows OS support for branch target injection mitigation is present” is “True” then the Windows Security update has been successfully installed.

The other red lines in that section simply confirm that more complete mitigation for Spectre requires firmware updates, which Intel says it’s in the process of rolling out. According to the company, updates for more than 90 percent of its processor products should be introduced by the end of next week.

Results for Meltdown protections

The second grouping — “Speculation control settings for CVE-2017-5754 [rogue data cache load] — refer to protections in place for the Meltdown vulneralbility. If you see the following results and no red lines then you’ve confirmed the Windows Security update has been successfully implemented and the machine is protected:

If you see any red lines in this section then that means the update has not been successfully applied. For more details on interpreting the PowerShell script output, Microsoft has a full results key here.

MacOS & iOS

Apple included mitigations to address Meltdown in its macOS 10.13.2 and iOS 11.2 updates released in December. It has since followed up with additional mitigations addressing Spectre with the just-issued macOS High Sierra 10.13.2 Supplemental Update and iOS 11.2.2 update.

What they address:

  • Meltdown (rogue data cache load — CVE-2017-5754)
  • Spectre variant 1 (bounds check bypass — CVE-2017-5753) to some degree
  • Spectre variant 2, (branch target injection — CVE-2017-5715) to some degree

What they dont’ address:

  • Spectre variants 1 and 2 — to some degree
    While Apple says its latest updates to macOS, iOS, and Safari help mitigate the risk of Spectre being exploited, the company acknowleges it will be continuing to develop and test further mitigations.

No reported compatibility or performance issues


After being left out of the loop, Linux developers are making significant progress on patches, even if they’re not particularly happy about being put in this position. The latest update of the stable Linux kernel (4.14.13) includes patches designed to mitigate Meltdown with Kernel Page Table Isolation (KPTI). More comprehensive patches (including fixes for ARM64 processors) will be available in 4.15, scheduled for release in two weeks.

Patches have also been added to the 4.4 and 4.9 stable kernel trees.

Canonical has released a second update for Ubuntu 16.04 LTS Xenial users after the first caused boot issues. You can find the new update with Linux kernel image 4.4.0-109 here.

What they address:

  • Meltdown (rogue data cache load — CVE-2017-5754), though not currently for 32bit (x86) machines 
  • Spectre variant 1 (bounds check bypass — CVE-2017-5753) to some degree
  • Spectre variant 2, (branch target injection — CVE-2017-5715) to some degree

What they dont’ address:

  • Meltdown for 32bit (x86) machines
  • Spectre variants 1 and 2 — to some degree
    Patches have now been released that mitigate both variants of Spectre, but variant 2 mitigation also requires firmware/microcode updates to be in place. Because those updates are still being (re)developed and rolled out — keep in mind the latest recommendation from Intel was not to apply its firmware patches — variant 2 mitigation is currently incomplete.Work is underway to implement Retpoline, a workaround mitigation technique introduced by Google specifically for dealing with Spectre variant 2. The big advantage of Retpoline appears to be that it results in less of a performance impact than the microcode fixes, but, that said, it does have limitations.For one thing, Retpoline does not work on Intel Skylake processors. More importantly, it requires that code be recompiled in order to “immunize” it. While recompiling the kernel with Retpoline is one thing, updating every userspace application is anything but a quick fix. As this FAQ on the Ubuntu Wiki puts it, “until every piece of code on a system is rebuilt with retpoline the kernel must use microcode-based mitigations to protect userspace.” In other words, Retpoline isn’t a complete substitution for applying microcode updates — yet.

Known issues:

  • Patches haven’t been released for machines running ARM64 processors: They are expected to be supported with the release of 4.15 in a couple of weeks.
  • Patches bricking Ubuntu 16.04 computers: According to Bleeping Computer, boot issues have been reported by a large number of Ubuntu users running the Xenial 16.04 series after updating to kernel image 4.4.0-108. New updates with kernel image 4.4.0-109 have since been released which address the issue.
  • No Meltdown fix is currently available for 32bit (x86): Moving to a 64-bit kernel is the only currently recommended mitigation.
  • Spectre version 2 mitigations still reliant on firmware updates: As Intel and AMD continue to work through update difficulties mitigation remains incomplete.
  • Performance impact: Based on initial testing, performance penalties for the patches are expected to range from single to double digits, depending primarily on how much interaction applications/workloads have with the kernel. You can find more details in benchmark studies conducted by Phoronix and Red Hat.

Checking Linux for Spectre and Meltdown vulnerability:

A simple script has been developed to help determine whether Linux kernel installations are still vulnerable to Meltdown and Spectre after applying patches. You can find it along with installation instructions here.


According to researchers, the most likely exploitation of Spectre appears to be web-based attacks using JavaScript (say in a malicious ad) to leak information, session keys, etc. cached in the browser. As such, Google, Mozilla, Apple, and Microsoft have all either issued or schedule new updates for their browsers to reduce that risk.

What browser updates address:

  • Spectre (CVE-2017-5753 and CVE-2017-5715) to some extent

What browser updates dont’ address:

  • Meltdown (CVE-2017-5754)
    You’ll need to apply OS updates to mitigate Meltdown. 


Google Chrome users are advised to turn on site isolation, which can help prevent a site from stealing data from another site.

Google has officially released Chrome 64 for Windows, Mac, and Linux. The update does include a patch to address Spectre, although Google did not provide technical details, stating simply “this release contains additional mitigations against speculative side-channel attack techniques.” In addition to those mitigations, the update also addresses other flaws (there are a total of 53 security fixes in all).


Mozilla has already issued Firefox version 57.0.4, which helps address Spectre by disabling or reducing Firefox’s internal timer functions and disabling the SharedArrayBuffer feature. Firefox users can take additional precaution by enabling site isolation, as well.


Apple has released Safari 11.0.2 to specifically mitigate the effects of Spectre.

IE and Edge

Microsoft has made changes to both Internet Explorer 11 and Microsoft Edge to mitigate Spectre. In addition to removing support for SharedArrayBuffer from Edge, it has made changes to reduce the precision of several time sources to make successful attacks more difficult.


OS and browser updates only partially mitigate Meltdown and Spectre. Organizations need to be prepared for UEFI firmware and BIOS updates, as well. When and whether updates will be pushed out will vary from vendor to vendor, adding another layer of complexity and uncertainty to patching. In some cases, admins may have to proactively check for updates from their PC makers periodically over the next few days or weeks.


Note: The saga surrounding Intel updates is long and ongoing. For the lastest news, skip down to “Known issues” and scroll to the bottom of the list.

UPDATE 1/12/18: Intel has released new Linux Processor microcode data files that can be used to add Meltdown and Spectre mitigations without having to perform a BIOS update.

Intel went on record promising firmware updates for 90 percent of affected processors made in the past five years on January 15. So far, it looks as though these microcode fixes apply to a specific list of processors provided here.

The microcode updates can be downloaded directly from Intel, and Bleeping Computer has provided instructions and a video example to help walk admins through the install process here. It should be noted that some issues have already been reported with the updates, specifically around unwanted reboots. While Intel initially confirmed machines with Broadwell and Haswell CPUs were experiencing that issue, later the company said machines running newer processors were affected, too (more details below).

Windows users need to wait until Microsoft finishes testing the microcode and releases an additional update.

Known issues:

  • Performance impact: Statements regarding the potential performance impact of those updates have been inconsistent, but the company has most recently said the patches are slowing processors down by six percent in certain situations. Intel has shared more details on performance impact based on specific workloads in a chart you can find here.
  • Older Broadwell and Haswell CPUs experiencing sudden reboots: Intel is already confirming the company has received reports of glitches resulting from the firmware update on systems running Intel Broadwell and Haswell CPUs.
  • Machines with newer CPUs also experiencing sudden reboots: Intel has since confirmed the firmware update is causing machines with Ivy Bridge, Sandy Bridge, Skylake, and Kaby Lake processors to suffer unwanted reboots, too. Intel now recommending customers NOT apply firmware update: The company has reportedly discovered the root cause of the Broadwell and Haswell boot issues, and is testing an updated patch. In the meantime, it is recommending customers stop deployment of the current patch to avoid reboots and other “unpredictable system behavior.” Recently Intel has issued a new microcode update for Skylake processors that addresses Spectre variant 2. Skylake system owners should expect firmware updates soon. Fixes for other chips remain in beta testing.
  • HP and Dell have removed latest BIOS updates until Intel issues new stable firmware: Following Intel’s advice, both companies have halted deployment of Intel’s buggy microcode.
  • Microsoft has issued an emergency out of band update (KB4078130) that disables Intel’s mitigation for Spectre variant 2: Microsoft justified the move by pointing to reports that Intel’s new microcode can cause higher than expected reboots which may result in data loss or corruption (confirmed in Intel’s Q4 2017 financial results statement).
  • UPDATE 2/21/18: Additional microcode updates addressing Spectre variant 2 available: Intel reports its microcode update for Skylake processors is stable, and additional updates for Kaby Lake and Coffee Lake are being rolled out, as well. Considering the problems experienced with the initial firmware updates, many experts are advising caution and careful testing before installing the new updates, however. According to Intel, fixes for Sandy Bridge, Ivy Bridge, Broadwell, and Haswell processors are still in beta. You can find the micocode patch update schedules for all Intel chips here.


AMD has officially acknowledged that its processors are vulnerable to both variants of Spectre, but not Meltdown. While the company says OS patches are enough to mitigate Spectre variant 1, it will be rolling out optional microcode updates this week, starting with fixes for Ryzen and EPYC processors.

Known issues:

  • Windows OS update compatibility issues: As first reported at the Verge, Microsoft has received numerous reports of PCs running AMD processors not booting after installing the latest Windows security update. After investigating, the company confirmed there are issues — specifically with AMD Opteron, Athlon, and AMD Turion X2 Ultra families — and temporarily stopped delivering the update to AMD devices. AMD says it is working with Microsoft to resolve the issue. In the meantime, affected users need to visit Microsoft’s support site for instructions on getting their machines back up and running.Microsoft has announced it will resume rolling out patches for AMD devices running Windows 7 SP1 and Windows Server 2008 R2 SP1, Windows 8.1 and Windows Server 2012 R2, and Windows 10, version 1709. Updates for four versions of Windows 10 — 1511, 1607, and 1703 — are still paused. As are updates for Windows Server 2016 and Windows 10 Enterprise.


According to IBM, firmware patches for POWER7+, POWER8, and POWER9 platforms are all currently available via FixCentral. The company says Power7 patches will be available February 7. In addition, it estimates IBM i operating system patches (also available via FixCentral) will finish rolling out on February 12, and AIX patches are available since January 26.


There is special worry about the cloud platforms that collectively host mission-critical workloads from millions of businesses, and data from hundreds of millions of consumers. First, the vulnerabilities can allow an attacker to bypass virtualized partitions, making it possible to steal data from all virtual machines on a single server. Second, there’s concern that in massive data center environments, the performance degradation from the patches would be exponentially replicated, leading to serious slowdowns of applications and web services.

  • As would be expected, cyber criminals have started to attempt to trick users into installing fake Spectre and Meltdown patches that are really malware, as Malwarebytes Labs recently warned.

What to do…What not to do?

Don’t Panic! The patches that have been issued so far by the OS vendors amount to mitigations and workarounds. The patches themselves are complex, and compatibility issues should be expected. For example, anti-virus software is deeply embedded in systems and kernels. A change in how kernel memory is stored will certainly affect anti-virus products.

Every company will have their own risks in terms of operational risk versus security risk. For that reason, I believe that it may be better for some organizations not to patch and instead use a different compensating control to mitigate exposure as much as possible.

Start and prepare for benchmark testing when patches come out to see how big of a performance impact it is going to make. Before you start, BACKUP, TEST YOUR BACKUP, and BACKUP AGAIN! 

There’s a greater sense of urgency with Spectre, because exploiting Meltdown requires having a foothold on the targeted system. Spectre opens up certain types of remote attack scenarios, which could result in compromising credentials and session keys, allowing hackers to bypass many security protections.

Reading other blogs it is apparent that applying patches to migtigate the risk may slow down the systems performance. This is not the case with everyone. It will vary for each business and type of operation.  For example, SQL is one of the most common type of database that are being used by businesses large and small. There is a significant I/O hit weather on-premise or in the Cloud. Read more about SQL Server performance with Spectre and Meltdown patches at SolidQ, but there are ways to address it.

For home users with newer Windows and Mac computers, the impact may be negligible. Systems with older processors are expected to see a bigger slowdown. Some servers could see a greater slowdown than PCs.

Over the next several months vendors will release and refine fixes. Only then can we be sure of the performance impact on various systems and configurations.

Keep in mind this is a Two-Part Solution

The specific solution for each system will vary by vendor and product. In most cases, two updates are needed to protect a system:

  • OS updates are coming fast from all major vendors.
  • Chipmaker microcode updates are being released as well. Most processors will need updates, but there are some exceptions.

Note that while Meltdown/Spectre can’t crash systems, some fixes can. Early problems have been reported with OS fixes in some scenarios. Also, some fixes require updates from app vendors, particularly antivirus solutions.

The Good News

There are no known exploits in the wild … yet! You still have time to get ahead of this thing.

Next Step

Secure your systems from Meltdown/Spectre vulnerabilities before sensitive data is exposed.

For even more info, Bleeping Computer has put together a good list of official advisories, notices, patches, and updates organized by vendor

Sources:  Microsoft | Intel | AMD | Barkly | Google | TheBleepingComputer | TheVerge