EUVD-2026-28550
GHSA-whfq-93mc-cv6g
CVSS VectorNVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Lifecycle Timeline
4DescriptionNVD
Instances deployed via the Proxmox extension allow unauthorized access to instances belonging to other tenants.
This issue affects Apache CloudStack: from 4.21.0.0 through 4.22.0.0.
The Proxmox extension for CloudStack improperly uses a user-editable instance setting, proxmox_vmid, to associate CloudStack instances with Proxmox virtual machines. Because this value is not restricted or validated against tenant ownership and Proxmox VM IDs are predictable, a non-privileged attacker can modify the setting to reference a VM belonging to another account. This allows unauthorized cross-tenant access and enables full control over the targeted VM, including starting, stopping, and destroying the virtual machine.
Users are recommended to upgrade to version 4.22.0.1, which fixes this issue.
As a workaround for the existing installations, editing of the proxmox_vmid instance detail by users can be prevented by adding this detail name to the global configuration parameter - user.vm.denied.details.
AnalysisAI
Unauthorized cross-tenant access in Apache CloudStack 4.21.0 through 4.22.0 allows remote unauthenticated attackers to gain full control over virtual machines belonging to other tenants via the Proxmox extension. Attackers exploit a user-editable 'proxmox_vmid' setting that lacks tenant ownership validation and predictable VM IDs to reference and control VMs across tenant boundaries, enabling VM start/stop/destroy operations. …
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RemediationAI
Within 24 hours: Identify all CloudStack deployments running versions 4.21.0-4.22.0 with Proxmox extension enabled; isolate affected clusters from external network access if possible. Within 7 days: implement network-level access controls restricting CloudStack API access to trusted administrative networks only; disable Proxmox extension functionality until patched. …
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