The Intel EPT paging code uses an optimization to defer flushing of any cached
EPT state until the p2m lock is dropped, so that multiple modifications done
under the same locked region only issue a single flush.
Freeing of paging structures however is not deferred until the flushing is
done, and can result in freed pages transiently being present in cached state.
Such stale entries can point to memory ranges not owned by the guest, thus
allowing access to unintended memory regions.
In the context switch logic Xen attempts to skip an IBPB in the case of
a vCPU returning to a CPU on which it was the previous vCPU to run.
While safe for Xen's isolation between vCPUs, this prevents the guest
kernel correctly isolating between tasks. Consider:
1) vCPU runs on CPU A, running task 1.
2) vCPU moves to CPU B, idle gets scheduled on A. Xen skips IBPB.
3) On CPU B, guest kernel switches from task 1 to 2, issuing IBPB.
4) vCPU moves back to CPU A. Xen skips IBPB again.
Now, task 2 is running on CPU A with task 1's training still in the BTB.
Shadow mode tracing code uses a set of per-CPU variables to avoid
cumbersome parameter passing. Some of these variables are written to
with guest controlled data, of guest controllable size. That size can
be larger than the variable, and bounding of the writes was missing.
Incorrect removal of permissions on PCI device unplug
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.
x86: Incorrect input sanitisation in Viridian hypercalls
[This CNA information record relates to multiple CVEs; the
text explains which aspects/vulnerabilities correspond to which CVE.]
Some Viridian hypercalls can specify a mask of vCPU IDs as an input, in
one of three formats. Xen has boundary checking bugs with all three
formats, which can cause out-of-bounds reads and writes while processing
the inputs.
* CVE-2025-58147. Hypercalls using the HV_VP_SET Sparse format can
cause vpmask_set() to write out of bounds when converting the bitmap
to Xen's format.
* CVE-2025-58148. Hypercalls using any input format can cause
send_ipi() to read d->vcpu[] out-of-bounds, and operate on a wil
x86: Incorrect input sanitisation in Viridian hypercalls
[This CNA information record relates to multiple CVEs; the
text explains which aspects/vulnerabilities correspond to which CVE.]
Some Viridian hypercalls can specify a mask of vCPU IDs as an input, in
one of three formats. Xen has boundary checking bugs with all three
formats, which can cause out-of-bounds reads and writes while processing
the inputs.
* CVE-2025-58147. Hypercalls using the HV_VP_SET Sparse format can
cause vpmask_set() to write out of bounds when converting the bitmap
to Xen's format.
* CVE-2025-58148. Hypercalls using any input format can cause
send_ipi() to read d->vcpu[] out-of-bounds, and operate on a wil
[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.
[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.
[This CNA information record relates to multiple CVEs; the
text explains which aspects/vulnerabilities correspond to which CVE.]
There are multiple issues related to the handling and accessing of guest
memory pages in the viridian code:
1. A NULL pointer dereference in the updating of the reference TSC area.
This is CVE-2025-27466.
2. A NULL pointer dereference by assuming the SIM page is mapped when
a synthetic timer message has to be delivered. This is
CVE-2025-58142.
3. A race in the mapping of the reference TSC page, where a guest can
get Xen to free a page while still present in the guest physical to
machine (
[This CNA information record relates to multiple CVEs; the
text explains which aspects/vulnerabilities correspond to which CVE.]
There are multiple issues related to the handling and accessing of guest
memory pages in the viridian code:
1. A NULL pointer dereference in the updating of the reference TSC area.
This is CVE-2025-27466.
2. A NULL pointer dereference by assuming the SIM page is mapped when
a synthetic timer message has to be delivered. This is
CVE-2025-58142.
3. A race in the mapping of the reference TSC page, where a guest can
get Xen to free a page while still present in the guest physical to
machine (
[This CNA information record relates to multiple CVEs; the
text explains which aspects/vulnerabilities correspond to which CVE.]
There are multiple issues related to the handling and accessing of guest
memory pages in the viridian code:
1. A NULL pointer dereference in the updating of the reference TSC area.
This is CVE-2025-27466.
2. A NULL pointer dereference by assuming the SIM page is mapped when
a synthetic timer message has to be delivered. This is
CVE-2025-58142.
3. A race in the mapping of the reference TSC page, where a guest can
get Xen to free a page while still present in the guest physical to
machine (
deadlock potential with VT-d and legacy PCI device pass-through
When setting up interrupt remapping for legacy PCI(-X) devices,
including PCI(-X) bridges, a lookup of the upstream bridge is required.
This lookup, itself involving acquiring of a lock, is done in a context
where acquiring that lock is unsafe. This can lead to a deadlock.
x86: Incorrect stubs exception handling for flags recovery
Certain instructions need intercepting and emulating by Xen. In some
cases Xen emulates the instruction by replaying it, using an executable
stub. Some instructions may raise an exception, which is supposed to be
handled gracefully. Certain replayed instructions have additional logic
to set up and recover the changes to the arithmetic flags.
For replayed instructions where the flags recovery logic is used, the
metadata for exception handling was incorrect, preventing Xen from
handling the the exception gracefully, treating it as fatal instead.
A transient execution vulnerability in some AMD processors may allow an attacker to infer data in the L1D cache, potentially resulting in the leakage of sensitive information across privileged boundaries.
A transient execution vulnerability in some AMD processors may allow an attacker to infer data from previous stores, potentially resulting in the leakage of privileged information.
Exposure of Sensitive Information in Shared Microarchitectural Structures during Transient Execution for some Intel(R) Processors may allow an authenticated user to potentially enable information disclosure via local access.
A cross-privilege Spectre v2 vulnerability allows attackers to bypass all deployed mitigations, including the recent Fine(IBT), and to leak arbitrary Linux kernel memory on Intel systems.
PVH guests have their ACPI tables constructed by the toolstack. The
construction involves building the tables in local memory, which are
then copied into guest memory. While actually used parts of the local
memory are filled in correctly, excess space that is being allocated is
left with its prior contents.