CVE-2026-23561
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · unedited[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.other_config: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:is_system_domain 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.other_config:storage_driver_domain 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:hvm_serial parameter, which should be restricted to the pool-admin role, as it can allow arbitrary dom0 file write.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceCVE-2026-23561 is a privilege escalation vulnerability in XenServer's XAPI where a vm-admin (a lower-privilege role) can set VM.other_config:storage_driver_domain to mark a VM as a storage domain for a PBD (Physical Block Device). This allows the vm-admin to manipulate storage connection states, as shutting down the marked VM causes the PBD to be erroneously marked as unplugged even when physically connected. This bypasses RBAC restrictions designed to limit storage configuration to higher-privileged roles.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Local
- Complexity
- Low
- Privileges
- None
- Authentication
- X
- User interaction
- None
- Scope
- X
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify vm-admin role usersRun 'xe subject-list' to list all users with RBAC roles, then run 'xe role-list' to map role names to UUIDs and identify which subjects have the vm-admin roleAffected if Any user with vm-admin role exists in the system, as this is the prerequisite role for exploiting this flaw
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Check for VMs with storage_driver_domain flagRun 'xe vm-param-get param-name=other_config param-key=storage_driver_domain' on each VM, or use 'xe vm-list other-config:storage_driver_domain=true' to find any VMs that have this flag setAffected if Any VM has storage_driver_domain set to true in its other_config, indicating it has been marked as a storage domain
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Verify VM-other_config modificationsRun 'xe vm-param-list uuid=<vm_uuid>' and inspect the other_config field for storage_driver_domain entries. Use audit logs if available to check for recent modifications to this keyAffected if storage_driver_domain appears in any VM's other_config and was not set by an administrator with full storage privileges
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Check for unexpected PBD unplug eventsReview PBD status using 'xe pbd-list' and look for PBDs that are marked as unplugged despite physical connection, particularly those associated with VMs that have storage_driver_domain setAffected if PBDs become unplugged in the system when VMs marked with storage_driver_domain are shut down, which is the behavioral symptom of this vulnerability
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Review RBAC role assignments for storage privilegesRun 'xe role-list' and cross-reference with 'xe subject-list' to verify which roles have storage-related permissions (pool-admin, admin roles) versus vm-admin roleAffected if Users with only vm-admin role have been able to modify storage-related VM configuration
A user is affected if they have users assigned the vm-admin role AND any VMs in their control have storage_driver_domain set to true in other_config, allowing unauthorized storage manipulation.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataApply XenServer patches for the cluster of RBAC vulnerabilities (CVE-2026-23559 through CVE-2026-23562 and CVE-2026-42486). Until patched, audit RBAC role assignments and monitor for unauthorized VM.other_config modifications.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-23561 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
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- Version or environment caveats, and links to real fixes
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