Vulnerability-Lookup

FKIE_CVE-2026-79609

Vulnerability from fkie_nvd - Published: 2026-10-13 16:17 - Updated: 2026-10-14 16:10

Severity

Summary

XPTI (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.

References

	URL	Tags
	security@xen.org	https://xenbits.xenproject.org/xsa/advisory-516.html
	af854a3a-2127-422b-91ae-364da2661108	http://xenbits.xen.org/xsa/advisory-516.html

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unknown",
          "product": "Xen",
          "vendor": "Xen",
          "versions": [
            {
              "status": "unknown",
              "version": "consult Xen advisory XSA-516"
            }
          ]
        }
      ],
      "source": "security@xen.org"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "XPTI (Xen Page Table Isolation) was introduced to mitigate Meltdown\n(CVE-2017-5754, one aspect of XSA-254).  This involves copying 64-bit PV\nguest page table entries from guest-chosen root page tables to the Xen-\nchosen one which is in actual use by hardware.  To read the guest root\npage table, the directmap is used.  PV guests, however, have a directmap\nwhich may not cover all memory; in particular this is the case if any\nmemory extends beyond the 5 TiB (CONFIG_BIGMEM=y: 3.5 TiB) address\nboundary."
    }
  ],
  "id": "CVE-2026-79609",
  "lastModified": "2026-10-14T16:10:14.750",
  "metrics": {},
  "published": "2026-10-13T16:17:23.147",
  "references": [
    {
      "source": "security@xen.org",
      "url": "https://xenbits.xenproject.org/xsa/advisory-516.html"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "http://xenbits.xen.org/xsa/advisory-516.html"
    }
  ],
  "sourceIdentifier": "security@xen.org",
  "vulnStatus": "Awaiting Analysis"
}

CVE-2026-79609 (GCVE-0-2026-79609)

Vulnerability from cvelistv5 – Published: 2026-10-13 15:44 – Updated: 2026-10-13 16:13

Title

x86: XPTI may break on huge-memory systems

Summary

Severity

No CVSS data available.

Assigner

XEN CNA under the mitre root

CNA scorecard D 56/100 over 46 records in the last 180 days details

References

2 references

URL	Tags
https://xenbits.xenproject.org/xsa/advisory-516.html
http://xenbits.xen.org/xsa/advisory-516.html

Impacted products

1 product

Vendor	Product	Version
Xen	Xen	Unknown: consult Xen advisory XSA-516

Date Public

2026-10-13 12:00

Credits

This issue was discovered by George Dunlap.

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "providerMetadata": {
          "dateUpdated": "2026-10-13T16:13:43.715Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "url": "http://xenbits.xen.org/xsa/advisory-516.html"
          }
        ],
        "title": "CVE Program Container"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unknown",
          "product": "Xen",
          "vendor": "Xen",
          "versions": [
            {
              "status": "unknown",
              "version": "consult Xen advisory XSA-516"
            }
          ]
        }
      ],
      "configurations": [
        {
          "lang": "en",
          "value": "All versions of Xen with the XPTI work backported to are affected.  In\nupstream these are Xen 4.7.5 and onwards, Xen 4.8.3 and onwards, Xen 4.9.2\nand onwards, Xen 4.10.1 and onwards, and all major releases from 4.11\nonwards.\n\nOnly 64-bit PV guests can leverage the vulnerability.  HVM and PVH guests\ncannot leverage the vulnerability.  32-bit PV guests haven\u0027t been security\nsupported anymore.\n\nOnly x86 systems are affected.  Arm systems are not affected.\n\nOnly systems with RAM above the 5 TiB (CONFIG_BIGMEM=y: 3.5 TiB) boundary\nare affected.  Systems with no RAM above the 5 TiB (CONFIG_BIGMEM=y: 3.5\nTiB) boundary are not affected."
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "This issue was discovered by George Dunlap."
        }
      ],
      "datePublic": "2026-10-13T12:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "XPTI (Xen Page Table Isolation) was introduced to mitigate Meltdown\n(CVE-2017-5754, one aspect of XSA-254).  This involves copying 64-bit PV\nguest page table entries from guest-chosen root page tables to the Xen-\nchosen one which is in actual use by hardware.  To read the guest root\npage table, the directmap is used.  PV guests, however, have a directmap\nwhich may not cover all memory; in particular this is the case if any\nmemory extends beyond the 5 TiB (CONFIG_BIGMEM=y: 3.5 TiB) address\nboundary."
        }
      ],
      "impacts": [
        {
          "descriptions": [
            {
              "lang": "en",
              "value": "A 64-bit PV guest may be able to elevate its privilege to that of the\nhost.  It is also possible for them to observe information pertaining to\nother guests, or to cause Denial of Service (DoS) affecting the entire\nhost."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-13T15:44:24.763Z",
        "orgId": "23aa2041-22e1-471f-9209-9b7396fa234f",
        "shortName": "XEN"
      },
      "references": [
        {
          "url": "https://xenbits.xenproject.org/xsa/advisory-516.html"
        }
      ],
      "title": "x86: XPTI may break on huge-memory systems",
      "workarounds": [
        {
          "lang": "en",
          "value": "Not running 64-bit PV guests will avoid the vulnerability.\n\nThe \"mem=\" hypervisor command line option may be used to limit the amount\nof memory Xen is going to use.  That would be \"mem=5T\" for the\nCONFIG_BIGMEM=n case and \"mem=3584G\" for the CONFIG_BIGMEM=y one."
        }
      ]
    }
  },
  "cveMetadata": {
    "assignerOrgId": "23aa2041-22e1-471f-9209-9b7396fa234f",
    "assignerShortName": "XEN",
    "cveId": "CVE-2026-79609",
    "datePublished": "2026-10-13T15:44:24.763Z",
    "dateReserved": "2026-08-25T07:35:05.289Z",
    "dateUpdated": "2026-10-13T16:13:43.715Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

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Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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