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.
Exploitability
AV:LAC:HPR:LUI:NScope
S:CImpact
C:HI:HA:H7.8/CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H