Information
Keep ESXi system properly patched.
By staying up to date on ESXi patches, vulnerabilities in the hypervisor can be mitigated. An educated attacker can exploit known vulnerabilities when attempting to attain access or elevate privileges on an ESXi host.
https://pubs.vmware.com/vsphere-65/topic/com.vmware.vsphere.update_manager.doc/GUID-D53B8D36-A8D7-4B3B-895C-929267508026.html
https://www.vmware.com/support/policies/security_response
NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.
Solution
From the vSphere web client select the host and click "Summary". Expand "Configuration" and verify "ESX/ESXi Version" and "Image Profile" strings. Those strings would tell you the current image version of the host. Ensure that the image version is the latest one given by VMware.