KubeVirt is a virtual machine management add-on for Kubernetes. In versions 0.59.0 and prior, if a malicious user has taken over a Kubernetes node where virt-handler (the KubeVirt node-daemon) is running, the virt-handler service account can be used to modify all node specs. This can be misused to lure-in system-level-privileged components which can, for instance, read all secrets on the cluster, or can exec into pods on other nodes. This way, a compromised node can be used to elevate privileges beyond the node until potentially having full privileged access to the whole cluster. The simplest way to exploit this, once a user could compromise a specific node, is to set with the virt-handler service account all other nodes to unschedulable and simply wait until system-critical components with high privileges appear on its node. No patches are available as of time of publication. As a workaround, gatekeeper users can add a webhook which will block the `virt-handler` service account to modify the spec of a node.

Affected: Go: kubevirt.io/kubevirt

### Impact

If a malicious user has taken over a Kubernetes node where virt-handler (the KubeVirt node-daemon) is running, the virt-handler service account can be used to modify all node specs.

This can be misused to lure-in system-level-privileged components (which can for instance read all secrets on the cluster, or can exec into pods on other nodes). This way a compromised node can be used to elevate privileges beyond the node until potentially having full privileged access to the whole cluster.

The simplest way to exploit this, once a user could compromise a specific node, is to set with the virt-handler service account all other nodes to unschedulable and simply wait until system-critical components with high privileges appear on its node.

Since this requires a node to be compromised first, the severity of this finding is considered Medium.

### Patches

Not yet available.

### Workarounds Gatekeeper users can add a webhook which will block the `virt-handler` service account to modify the spec of a node.

An example policy, preventing virt-handler from changing the node spec may look like this:

```yaml apiVersion: templates.gatekeeper.sh/v1 kind: ConstraintTemplate metadata: name: virthandlerrestrictions spec: [...] targets: - libs: - | [...] is_virt_handler(username) { username == "system:serviceaccount:kubevirt:virt-handler" } mutates_node_in_unintended_way { # TODO…

kubevirt-container-disk-0.59.0-2.1 on GA media