x86: XPTI may break on huge-memory systems

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-79609
StatePUBLISHED
AssignerXEN
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-13 16:17:23 UTC
Updated2026-10-14 16:10:14 UTC
DescriptionXPTI (Xen Page Table Isolation) was introduced to mitigate Meltdown (CVE-2017-5754, one aspect of XSA-254). This involves copying 64-bit PV guest page table entries from guest-chosen root page tables to the Xen- chosen one which is in actual use by hardware. To read the guest root page table, the directmap is used. PV guests, however, have a directmap which may not cover all memory; in particular this is the case if any memory extends beyond the 5 TiB (CONFIG_BIGMEM=y: 3.5 TiB) address boundary.

Risk And Classification

EPSS: 0.001590000 probability, percentile 0.045460000 (date 2026-10-14)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Xen Xen unknown consult Xen advisory XSA-516 Not specified

References

ReferenceSourceLinkTags
xenbits.xen.org/xsa/advisory-516.html af854a3a-2127-422b-91ae-364da2661108 xenbits.xen.org
xenbits.xenproject.org/xsa/advisory-516.html [email protected] xenbits.xenproject.org
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: This issue was discovered by George Dunlap. (en)

Additional Advisory Data

Workarounds

CNA: Not running 64-bit PV guests will avoid the vulnerability. The "mem=" hypervisor command line option may be used to limit the amount of memory Xen is going to use. That would be "mem=5T" for the CONFIG_BIGMEM=n case and "mem=3584G" for the CONFIG_BIGMEM=y one.

© CVE.report 2026

Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties, implied or otherwise, with regard to this information or its use. Any use of this information is at the user's risk. It is the responsibility of user to evaluate the accuracy, completeness or usefulness of any information, opinion, advice or other content. EACH USER WILL BE SOLELY RESPONSIBLE FOR ANY consequences of his or her direct or indirect use of this web site. ALL WARRANTIES OF ANY KIND ARE EXPRESSLY DISCLAIMED. This site will NOT BE LIABLE FOR ANY DIRECT, INDIRECT or any other kind of loss.

CVE, CWE, and OVAL are registred trademarks of The MITRE Corporation and the authoritative source of CVE content is MITRE's CVE web site. This site includes MITRE data granted under the following license.

Free CVE JSON API cve.report/api

CVE.report and Source URL Uptime Status status.cve.report