VSA-2025-008: XSA-476 - Xen Vulnerability
| Published | Updated | Severity | CVSS 4.0 | Affected products |
|---|---|---|---|---|
| 2025-10-24 | 2025-12-18 | 🟢 Low | Not available yet | - None |
An XSA and its associated CVE were published. For Vates products, we classify the impact as Low, as PCI Hotplug is not a supported feature in XCP-ng. For details on how we assign severity levels, see our Severity Levels Explained page.
Summary
The Xen project recently disclosed one vulnerability affecting Xen 4.0 and newer. When passing through PCI devices, the detach logic in libxl won't remove access permissions to any 64bit memory BARs the device might have. As a result a domain can still have access any 64bit memory BAR when such device is no longer assigned to the domain.
- For PV domains the permission leak allows the domain itself to map the memory in the page-tables.
- For HVM it would require a compromised device model or stubdomain to map the leaked memory into the HVM domain p2m.
Impact
A buggy or malicious PV guest can access memory of PCI devices no longer assigned to it.
Affected Versions
- None
Mitigation
We do not offer mitigation because we do not support PCI hotplug/hot unplugging so the vulnerability is not deemed exploitable.
Resolution
As a defense-in-depth measure, we included the fix for this vulnerability in the December 2025 Security and Maintenance update. Our Xen packages starting from version 4.17.5-23.1 contain this fix.
Credits
This issue was discovered by Jiqian Chen of AMD and diagnosed as a security issue by Roger Pau Monné of XenServer.