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Zombieload – Critical Linux CVE Affects Almost All Intel CPUs

June 10, 2019 - TuxCare PR Team

Critical MDS affects almost all Intel CPUs

  1. What is Zombieload Vulnerability?
  2. What is MDS attack?
  3. Which CPUs are affected by Zombieload?
  4. How to mitigate the MDS/Zombieload Vulnerability?
  5. MDS/Zombieload Vulnerability Patch Release Schedule


What is Zombieload Vulnerability?

Linux vulnerabilities are becoming like celebrities, with freaky names and their own websites.

The latest ones to hit the scene are Zombieload, RIDL and Fallout, also known as Microarchitectural Data Sampling, (MDS for short), discovered by Intel and researched by academic departments at security-focused institutions around the world. These vulnerabilities are in the same vein as Spectre and Meltdown, being design flaws that reveal data. Zombieload is particularly worrying because it affects all Intel Core and Xeon CPUs manufactured since 2011.


What is MDS Attack?

Microarchitectural Data Sampling (MDS) attack is the type of attack that can reveal private data by breaking the privacy borders between apps.

Watch the video with the insights regarding MDS from Igor Seletskiy below, or scroll down for instructions on how to mitigate the MDS/Zombieload Vulnerability with no rebooting required.


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There are four distinct vulnerability registrations combining to make a Zombieload exploit possible: CVE–2018–12126, CVE–2018–12127, CVE–2018–12130, and CVE–2019–11091. Look at the codes and you’ll see three were registered last year. The issue has been kept under wraps, a practice known as Coordinated Disclosure, to stop ‘bad actors’ exploiting vulnerabilities before the rest of us can defend against them. Microsoft, Amazon AWS and Google have all mitigated the problem in their data centers, being in the ‘inner circle’ of companies benefiting from advance notice of such problems. Anyone else has to wait for an update from their OS vendor.


Which CPUs Are Affected by Zombieload?

Researchers behind ZombieLoad: Cross-Privilege-Boundary Data Sampling study has tested multiple Intel CPUs and found out that at least the following CPUs are vulnerable to Zombieload and the rest of MDS pack of vulnerabilities:

CPU (Stepping) µ-arch.
Core i7-3630QM (E1) Ivy Bridge
Lab Core i7-6700K (R0) Skylake-S
Lab Core i5-7300U (H0) Kaby Lake
Lab Core i7-7700 (B0) Kaby Lake
Lab Core i7-8650U (Y0) Kaby Lake-R
Lab Core i7-8565U (W0) Whiskey Lake
Lab Core i7-8700K (U0) Coffee Lake-S
Lab Core i9-9900K (P0) Coffee Lake-R
Lab Xeon E5-1630 v4 (R0) Broadwell-EP
Cloud Xeon E5-2670 (C2) Sandy Bridge-EP
Cloud Xeon Gold 5120 (M0) Skylake-SP
Cloud Xeon Platinum 8175M (H0) Skylake-SP
Cloud Xeon Gold 5218 (B1) Cloud Xeon Gold 5218 (B1)



How to mitigate the MDS/Zombieload Vulnerability

If you are running on hardware:

To mitigate this vulnerability, you will need to take 3 steps that require no reboot if you follow the instructions below:

Step 1: Update Microcode without a reboot

Microcode is the code that runs inside the CPU itself and is handled by Intel. Microcode update is usually done on reboot: you get the new kernel, it will have new microcode and when the kernel boots it will install new microcode into CPU. You can update microcode without reboot using our instructions.

Step 2: Disable Hyperthreading without a reboot

If you don’t disable the CPU simultaneous multithreading (SMT) – you will still have an issue that attacker can read the data of the same CPU. With KernelCare you can disable Hyperthreading without a reboot using our instructions.

Step 3: Apply KernelCare patches

Even if you have done steps 1 and 2, you must still update the Linux Kernel to ensure that the local user can not read the data you are running on the CPU. With KernelCare you can do that without rebooting. Sign up for the free 7-day trial.

If you are running on a Virtual Machine:

You only need to patch the Linux Kernel inside the VM. Make sure that your host node is updated as well which is typically done by your service provider.

If you are using your KernelCare – your patches will be delivered automatically by KernelCare and you don’t need to do anything extra. If not – this is the right time to sign up for the free 7-day trial.


KernelCare started testing live patches for MDS on Friday, May 17, and they are now rolled out for all main distributions, with others shortly to follow. For the latest news, follow us on @KernelCare.

Get a FREE 7-Day Supported Trial of KernelCare 



MDS/Zombieload Vulnerability Patch Release Schedule

Updated Monday, June 10

The KernelCare patch release schedule is shown below. Release schedules are subject to change. Check here regularly or get in touch with our helpdesk.

Released to production:

  • CentOS 6
  • CentOSPlus for CentOS 6
  • CloudLinux OS 6
  • Debian 8
  • Debian 9
  • Ubuntu 14.04 LTS (Trusty Tahr)
  • Ubuntu 16.04 LTS (Xenial Xerus)
  • Ubuntu 18.04 LTS (Bionic Beaver)
  • Oracle Enterprise Linux 6
  • Oracle Enterprise Linux 7
  • Oracle UEK 3
  • Oracle UEK 4
  • Oracle UEK 5
  • OpenVZ
  • Proxmox VE
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7
  • Amazon Linux 1
  • Amazon Linux 2

Patches from the production feed will be applied automatically.

Released to the test feed:

  • CentOS 7
  • CentOSPlus for CentOS 7
  • Cloud Linux 6 hybrid

To install patches from the test feed, run the command:

kcarectl --test --update

When production updates are available, KernelCare will use the regular feed automatically.

Due Week 24:

  • CentOS 7
  • CentOSPlus for CentOS 7
  • CloudLinux OS 7
  • Oracle Enterprise Linux

Read more on how KernelCare address other critical vulnerabilities:

  1. Zombieload 2: KernelCare Team is on it!
  2. SWAPGS: KernelCare patches on the way
  3. SACK Panic & Slowness: KernelCare Live Patches Are Here
  4. RIDL – Another MDS Attack that Live Patching Would Have Saved You From
  5. Fallout – the MDS Side Channel Attack That Isn’t Zombieload
  6. QEMU-KVM vhost/vhost_net Guest to Host Kernel Escape Vulnerability
  7. CVE–2018–1000199 patches
  8. Intel DDIO ‘NetCat’ Vulnerability

Looking to automate vulnerability patching without kernel reboots, system downtime, or scheduled maintenance windows?

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