Unrated

XAPI VM.platform:hvm_serial RBAC privilege escalation

IdentifiersCVE-2026-42486CWE-269

CVE-2026-42486 is an RBAC enforcement flaw in XAPI, tracked in Xen Security Advisory XSA-489. A user with the lower-privileged vm-admin role can set the sensitive VM.platform:hvm_serial parameter even though modification of that key should be restricted to the pool-admin role. The issue stems from insufficient per-key authorization checks in the VM.platform setter path, allowing a privileged-but-not-fully-privileged administrator to modify a platform key whose security impact exceeds the general field-level permission model. The advisory and associated fix note that hvm_serial can enable arbitrary file write in dom0, making this an XAPI privilege-boundary bypass rather than a generic configuration weakness.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows a vm-admin to exceed intended RBAC restrictions and effectively escalate privileges toward pool-admin-equivalent impact. Because the hvm_serial parameter can permit arbitrary dom0 file write, the flaw can lead to compromise of the control domain, with consequent risk to host integrity and management-plane trust. In practical terms, this can enable modification of files on dom0 and facilitate broader host-level compromise.

Mitigation

If you can’t patch tonight, do this now.

Until patched, disable RBAC subjects assigned lower-privileged administrator roles implicated by XSA-489, specifically vm-admin, vm-power-admin, or pool-operator, where operationally feasible. More specifically for this CVE, avoid assigning vm-admin to untrusted users in pools where RBAC is enabled, because the vulnerability is exposed only when non-fully-privileged administrative roles are in use.

Remediation

Patch, then assume compromise.

Apply the XAPI fixes referenced by XSA-489. The content states that the fixes were merged and backported and are available in XAPI releases v26.12.0 and v26.1.11. The underlying remediation is to enforce per-key RBAC checks on VM.platform setters so that sensitive keys such as hvm_serial are restricted to pool-admin. Upgrade affected XAPI/Xen-based platforms to vendor-provided builds containing these fixes.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

ACTIVITY FEED

Recent activity

7 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

7 SOURCESView more in app

runzero blogNews

Apr 30, 2026

XCP-ng vulnerabilities: How to find impacted assets

One of the confirmed actionable XAPI RBAC escalation vulnerabilities discussed in XSA-489/VSA-2026-011.

runzero blogNews

Sep 25, 2024

Citrix Hypervisor vulnerabilities: How to find affected assets

One of five actionable XAPI RBAC escalation vulnerabilities confirmed in XSA-489.

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Exposure mapping

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Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity5