CVE-2026-42486: Multiple RBAC issues in XAPI

[This CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] XAPI can configure different users with different roles, using Role Based Access Control. For more details, see:

https://docs.xenserver.com/en-us/xencenter/current-release/rbac-overview.html#rbac-roles

The pool-admin role is fully privileged. Notably, users with this role can also SSH into the host as root.

The other administrator roles are pool-operator, vm-power-admin and vm-admin, each of which are authorised to configure and manage various aspects of the system.

Some settings are inadequately restricted, and can be set by a lower privilege of administrator than expected.

CVE-2026-23559: A vm-admin can set VBD.otherconfig:backend-local and turn arbitrary files in dom0 into VDIs (virtual disks) and give said disks to a VM they control. This is an arbitrary read and/or modify of files in dom0.

CVE-2026-23560: A vm-admin can set VM.other-config:issystemdomain and mark a VM as a system domain. System domains are ignored and left running during certain other host/pool operations, and may be hidden from view in tooling.

CVE-2026-23561: A vm-admin can set VM.otherconfig:storagedriverdomain and mark a VM as the storage domain for a particular host storage connection (PBD). Shutting down the VM can cause the PBD to be erroneously marked as unplugged when it is not.

CVE-2026-23562: Configuration of PCI passthrough is normally restricted to the pool-admin role. However one API was missing this check, allowing a vm-admin access to unintended host hardware.

CVE-2026-42486: A vm-admin can set the VM.platform:hvmserial parameter, which should be restricted to the pool-admin role, as it can allow arbitrary dom0 file write.