[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.

race in VT-d domain ID cleanup Xen domain IDs are up to 15 bits wide. VT-d hardware may allow for only less than 15 bits to hold a domain ID associating a physical device with a particular domain. Therefore internally Xen domain IDs are mapped to the smaller value range. The cleaning up of the housekeeping structures has a race, allowing for VT-d domain IDs to be leaked and flushes to be bypassed.

x86 pv: Race condition in typeref acquisition Xen maintains a type reference count for pages, in addition to a regular reference count. This scheme is used to maintain invariants required for Xen's safety, e.g. PV guests may not have direct writeable access to pagetables; updates need auditing by Xen. Unfortunately, the logic for acquiring a type reference has a race condition, whereby a safely TLB flush is issued too early and creates a window where the guest can re-establish the read/write mapping before writeability is prohibited.

Another race in XENMAPSPACE_grant_table handling Guests are permitted access to certain Xen-owned pages of memory. The majority of such pages remain allocated / associated with a guest for its entire lifetime. Grant table v2 status pages, however, are de-allocated when a guest switches (back) from v2 to v1. Freeing such pages requires that the hypervisor enforce that no parallel request can result in the addition of a mapping of such a page to a guest. That enforcement was missing, allowing guests to retain access to pages that were freed and perhaps re-used for other purposes. Unfortunately, when XSA-379 was being prepared, this similar issue was not noticed.

grant table v2 status pages may remain accessible after de-allocation Guest get permitted access to certain Xen-owned pages of memory. The majority of such pages remain allocated / associated with a guest for its entire lifetime. Grant table v2 status pages, however, get de-allocated when a guest switched (back) from v2 to v1. The freeing of such pages requires that the hypervisor know where in the guest these pages were mapped. The hypervisor tracks only one use within guest space, but racing requests from the guest to insert mappings of these pages may result in any of them to become mapped in multiple locations. Upon switching back from v2 to v1, the guest would then retain access to a page that was freed and perhaps re-used for other purposes.

The EVTCHNOP_expand_array hypercall checks for whether FIFO event channels are enabled, but without holding the correct lock. It can race with EVTCHNOP_reset, resulting in dereferencing a NULL pointer.

Accessing the vNUMA configuration data of a guest is still possible when domain destruction has already started. The cleaning up of that configuration information is not synchronized with its retrieval by a device model controlling the guest.

Accesses to the CMOS memory contents are done using an indirect IO port pair. Therefore Xen needs to cache the guest chosen index, and one of the usages of the index didn't take the necessary locking to avoid concurrent changes. As a result, a guest could change the index after it being checked, causing a subsequent out-of-bound read access to the contents of an array.

A Speculative Race Condition (SRC) vulnerability that impacts modern CPU architectures supporting speculative execution (related to Spectre V1) has been disclosed. An unauthenticated attacker can exploit this vulnerability to disclose arbitrary data from the CPU using race conditions to access the speculative executable code paths.

HVM guest I/O port accesses are subject to either emulation or at least translation. Translations are managed by the device model (via XEN_DOMCTL_ioport_mapping), and hence the linked list used may changed at any time. Traversal of those lists (while handling guest I/O port accesses) therefore needs synchronizing with updates, which was missing so far.

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.

[This CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] There are two issues related to the mapping of pages belonging to other domains: For one, an assertion is wrong there, where the case actually needs handling. A NULL pointer de-reference could result on a release build. This is CVE-2025-58144. And then the P2M lock isn't held until a page reference was actually obtained (or the attempt to do so has failed). Otherwise the page can not only change type, but even ownership in between, thus allowing domain boundaries to be violated. This is CVE-2025-58145.