Xen CVE-2026-62435

[This CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.]

With the introduction of Grant Table v2 came the requirement to be able to switch between versions. Switching from v1 to v2 reduces the number of valid grant references, as a bigger shared entry structure is then needed while the shared table doesn't change size. Switching from v2 back to v1 the status frames, which are separate in v2, go away.

Code holding, but intermediately dropping and then re-acquiring the grant table lock, sometimes wrongly assumes that said properties wouldn't change across the window in time where the lock is not being held.

The v1 -> v2 issue is CVE-2026-62435.

The v2 -> v1 issue is CVE-2026-62436.

Xen hypervisor versions supporting Grant Table v2 and the ability to switch between v1 and v2. The specific version ranges are detailed in the Xen Security Advisory XSA-501 (https://xenbits.xenproject.org/xsa/advisory-501.html). All Xen deployments using grant tables (common for PV drivers) are potentially affected if v2 is enabled and version switching is possible.