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title: "esx.problem.hyperthreading.unmitigated, after upgrading to 6.5.0 U2 ESXi650-201810002"
canonical: "https://www.virtcloudrocks.com/space/vblog01/blog/721322/esx.problem.hyperthreading.unmitigated%2C%20after%20upgrading%20to%206.5.0%20U2%20ESXi650-201810002"
format: markdown
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Few days ago I did an upgrade to our VMware ESXi hosts to the latest patched version of the vSphere 6.5.0 U2 (Release name:  ESXi650-201810002 - Build No:  10390116 ). After the upgrade was finished I noticed that on the upgraded host I was receiving a warning message, esx.problem.hyperthreading.unmitigated After some research I found out that this was warning is related with the patch that VMware has done to mitigate the CVE-2018-3646 vulnerability. The ESXi patches available in VMSA-2018-0020 to mitigate CVE-2018-3646 introduced a new notification to indicate the remediation status of the 'L1 Terminal Fault' (L1TF - VMM) vulnerability. To remediate this warning, you should follow the VMware  KB55806 ,  Below an excerpt from the Kb article that shows how it can be enabled the  ESXi Side-Channel-Aware Scheduler  using the vSphere Web Client or vSphere Client, Connect to the vCenter Server using either the vSphere Web or vSphere Client. Select an ESXi host in the inventory. Click the  Manage  (5.5/6.0) or Configure (6.5/6.7) tab. Click the  Settings  sub-tab. Under the System heading, click  Advanced System Settings . Click in the Filter box and search  VMkernel.Boot.hyperthreadingMitigation Select the setting by name and click the  Edit  pencil icon. Change the configuration option to true (default: false). Click  OK . Reboot the ESXi host for the configuration change to go into effect. In case that after internal risk assessment you decide not to enable the ESXi Side-Channel-Aware Scheduler, you can suppress the  esx.problem.hyperthreading.unmitigated  notification, by changing the value of the ESXi advanced option  UserVars.SuppressHyperthreadWarning  from 0 to 1.  Related articles VMware response to ‘L1 Terminal Fault - VMM’ (L1TF - VMM) Speculative-Execution vulnerability in Intel processors for vSphere: CVE-2018-3646 (55806) https://kb.vmware.com/s/article/55806 Build numbers and versions of VMware ESXi/ESX (2143832) https://kb.vmware.com/s/article/2143832 “esx.problem.hyperthreading.unmitigated” notification displayed in vCenter Server after applying updates for CVE-2018-3646 (57374) https://kb.vmware.com/s/article/57374