CVE-2026-23558: Xen

High severity, CVSS 7.8. EPSS: 0.1% chance of exploitation in the next 30 days.

The adjustments made for XSA-379 as well as those subsequently becoming XSA-387 still left a race window, when a HVM or PVH guest does a grant table version change from v2 to v1 in parallel with mapping the status page(s) via XENMEM_add_to_physmap. Some of the status pages may then be freed while mappings of them would still be inserted into the guest's secondary (P2M) page tables.

Affected products

• Xen Xen: from 4.0.0

Published 2026-05-19. Last modified 2026-06-17.