On a compromised node, the virt-handler service account can be used to modify all node specs
Date: 2023-03
Affected: go/kubevirt.io/kubevirt
Attack vector: auth-bypass
Category: vulnerability-disclosure
Severity: High
CVE: CVE-2023-26484
CWE: CWE-863
CVSS: 8.2 (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N)

### 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


Mitigations:

Architectural layers (MAESTRO):