EUVD-2026-63847
GHSA-qh8m-g3r9-6vh2
Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Reachable via public API with only default User role (PR:L, AV:N, AC:L, UI:N); root RCE on the shared hypervisor breaks tenant isolation, so scope changes (S:C) with full C/I/A impact.
Primary rating from Vendor (apache).
CVSS VectorVendor: apache
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
2DescriptionCVE.org
SSRF via Metalink Mirror URL Resolution:
An authenticated tenant can register a template pointing to an attacker-controlled metalink file containing internal targets. The Secondary Storage VM will retrieve the data and persist it as a template file, which can later be downloaded through normal APIs.
RCE on KVM hypervisor via NFS, Metalink files with/without Direct Downloads:
An authenticated CloudStack tenant holding the default User role can execute arbitrary shell commands as root on the KVM hypervisor host that runs other tenants' VMs. This is cross-tenant root on the underlying compute, reachable via the public CloudStack API.
When a User registers a VM template with directDownload=true and a URL pointing to a .metalink file, the management server fetches the metalink XML and dispatches download to the KVM agent. Inner URLs inside the metalink XML are never re-validated against the scheme allowlist.
These issues affect Apache CloudStack: from 4.14.0.0 through 4.20.3.0 and from 4.21.0.0 through 4.22.1.0.
Users are recommended to upgrade to version 4.20.3.1 or 4.22.1.1 or later, which fixes the issue.
Articles & Coverage 2
AnalysisAI
Cross-tenant root command execution in Apache CloudStack (4.14.0.0-4.20.3.0 and 4.21.0.0-4.22.1.0) allows an authenticated tenant holding only the default User role to run arbitrary shell commands as root on the KVM hypervisor host, which also runs other tenants' VMs. The flaw stems from CloudStack fetching a user-supplied .metalink file during directDownload template registration and dispatching its inner URLs to the KVM agent without re-validating them against the scheme allowlist; a related SSRF variant lets the Secondary Storage VM retrieve internal targets and persist them as downloadable templates. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Requires a valid authenticated CloudStack account with the default User role and access to the public CloudStack API - no admin rights are needed. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | This is a genuine high-priority issue rather than a high-CVSS-but-low-impact finding: the attacker only needs the default User role reachable through the public CloudStack API, and the outcome is arbitrary root command execution on the shared KVM host that runs other tenants' workloads - a full breach of tenant isolation on the compute plane. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Vendor-released patch: upgrade to Apache CloudStack 4.20.3.1 or 4.22.1.1 (or later), which re-validate Metalink inner URLs against the scheme allowlist; see the advisory at https://lists.apache.org/thread/g6cwddtjrwbh1d56wjz4cfp3fzfm4kbc. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Inventory all CloudStack deployments to identify affected versions (4.14.0.0-4.20.3.0 and 4.21.0.0-4.22.1.0); immediately restrict template registration permissions to administrative users only and disable the directDownload feature in CloudStack settings if operationally feasible. …
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External POC / Exploit Code
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