x86 shadow paging is deprecated

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-42493
StatePUBLISHED
AssignerXEN
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-28 13:18:32 UTC
Updated2026-07-28 17:16:39 UTC
DescriptionAddressing certain issues, in particular related to operations which may take excessively long and therefore would need preemption, has turned out overly costly. Since alternatives (HVM/PVH: HAP, PV: shim) are commonly available, the decision was to deprecate the functionality, while still retaining it for people to use at their own (security) risk. Memory-wise small enough guests may still be okay to run.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.004740000 probability, percentile 0.383970000 (date 2026-07-29)

Problem Types: CWE-400 | CWE-400 CWE-400 Uncontrolled Resource Consumption

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Xen Xen unknown consult Xen advisory XSA-495 Not specified

References

ReferenceSourceLinkTags
www.openwall.com/lists/oss-security/2026/07/28/12 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com
xenbits.xen.org/xsa/advisory-495.html af854a3a-2127-422b-91ae-364da2661108 xenbits.xen.org
xenbits.xenproject.org/xsa/advisory-495.html [email protected] xenbits.xenproject.org
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Additional Advisory Data

Workarounds

CNA: Running HVM and PVH in Hardware Assisted Paging (HAP) mode will avoid this vulnerability. There's no mitigation available for PV guests. This is because shadow mode, if support is enabled in the hypervisor, could be engaged at any time. Note that without shadow mode built into Xen, guests not properly dealing with L1TF will simply be crashed instead.

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