Vulnerability-Lookup

ubuntu-cve-2026-79603

Vulnerability from osv_ubuntu

Published

2026-09-08 12:00

Modified

2026-09-10 09:05

Summary

Details

x86 PV guests can free memory pages while still keeping a stale TLB entry pointing to them. A TLB flush is only issued by Xen (if needed) when the page is re-used. Since it's possible for the page to be scrubbed ahead of the TLB flush, there's a window where a PV guest can modify an already scrubbed page. Deployments using xsm=silo scrub-domheap with the aim of not allowing the exchange of information amongst guests are not effective in the presence of PV guests. All Xen versions from 4.13 onwards are vulnerable. Xen versions 4.12 and earlier are not vulnerable as they lack the scrub-domheap command line option. Only x86 PV guests can exploit the vulnerability.

Severity

4.3 (Medium)


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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-79603	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-79603	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
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            "binary_version": "4.6.5-0ubuntu1.4"
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            "binary_version": "4.6.5-0ubuntu1.4"
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          },
          {
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          },
          {
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          },
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      "versions": [
        "4.20.0+68-g35cb38b222-1",
        "4.20.2+7-g1badcf5035-2",
        "4.20.2+7-g1badcf5035-2build2"
      ]
    }
  ],
  "aliases": [],
  "details": "x86 PV guests can free memory pages while still keeping a stale TLB entry pointing to them.  A TLB flush is only issued by Xen (if needed) when the page is re-used.  Since it\u0027s possible for the page to be scrubbed ahead of the TLB flush, there\u0027s a window where a PV guest can modify an already scrubbed page. Deployments using `xsm=silo scrub-domheap` with the aim of not allowing the exchange of information amongst guests are not effective in the presence of PV guests. All Xen versions from 4.13 onwards are vulnerable.  Xen versions 4.12 and earlier are not vulnerable as they lack the `scrub-domheap` command line option. Only x86 PV guests can exploit the vulnerability.",
  "id": "UBUNTU-CVE-2026-79603",
  "modified": "2026-09-10T09:05:18Z",
  "published": "2026-09-08T12:00:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-79603"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-79603"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-79603"
  ]
}

CVE-2026-79603 (GCVE-0-2026-79603)

Vulnerability from cvelistv5 – Published: 2026-09-08 12:11 – Updated: 2026-09-08 17:08

Title

Unconditionally do TLB flushing ahead of page scrubbing

Summary

Severity

4.3 (Medium)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-08 13:42 UTC

CWE

CWE-664 - Improper Control of a Resource Through its Lifetime

Assigner

XEN mitre root

References

3 references

URL	Tags
https://xenbits.xenproject.org/xsa/advisory-511.html
http://xenbits.xen.org/xsa/advisory-511.html
http://www.openwall.com/lists/oss-security/2026/09/08/8

Impacted products

1 product

Vendor	Product	Version
Xen	Xen	Unknown: consult Xen advisory XSA-511

Date Public

2026-09-08 12:00

Credits

This issue was discovered by Roger Pau Monné of AMD.

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "providerMetadata": {
          "dateUpdated": "2026-09-08T17:08:33.807Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "url": "http://xenbits.xen.org/xsa/advisory-511.html"
          },
          {
            "url": "http://www.openwall.com/lists/oss-security/2026/09/08/8"
          }
        ],
        "title": "CVE Program Container"
      },
      {
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "LOW",
              "attackVector": "NETWORK",
              "availabilityImpact": "NONE",
              "baseScore": 4.3,
              "baseSeverity": "MEDIUM",
              "confidentialityImpact": "LOW",
              "integrityImpact": "NONE",
              "privilegesRequired": "LOW",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N",
              "version": "3.1"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2026-79603",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-08T13:42:37.092287Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "problemTypes": [
          {
            "descriptions": [
              {
                "cweId": "CWE-664",
                "description": "CWE-664 Improper Control of a Resource Through its Lifetime",
                "lang": "en",
                "type": "CWE"
              }
            ]
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-09-08T13:42:41.424Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unknown",
          "product": "Xen",
          "vendor": "Xen",
          "versions": [
            {
              "status": "unknown",
              "version": "consult Xen advisory XSA-511"
            }
          ]
        }
      ],
      "configurations": [
        {
          "lang": "en",
          "value": "All Xen versions from 4.13 onwards are vulnerable.  Xen versions 4.12 and\nearlier are not vulnerable as they lack the `scrub-domheap` command line\noption.\n\nOnly x86 PV guests can exploit the vulnerability."
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "This issue was discovered by Roger Pau Monn\u00e9 of AMD."
        }
      ],
      "datePublic": "2026-09-08T12:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "x86 PV guests can free memory pages while still keeping a stale TLB entry\npointing to them.  A TLB flush is only issued by Xen (if needed) when the\npage is re-used.  Since it\u0027s possible for the page to be scrubbed ahead of\nthe TLB flush, there\u0027s a window where a PV guest can modify an already\nscrubbed page."
        }
      ],
      "impacts": [
        {
          "descriptions": [
            {
              "lang": "en",
              "value": "Deployments using `xsm=silo scrub-domheap` with the aim of not allowing the\nexchange of information amongst guests are not effective in the presence of\nPV guests."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-08T12:11:21.789Z",
        "orgId": "23aa2041-22e1-471f-9209-9b7396fa234f",
        "shortName": "XEN"
      },
      "references": [
        {
          "url": "https://xenbits.xenproject.org/xsa/advisory-511.html"
        }
      ],
      "title": "Unconditionally do TLB flushing ahead of page scrubbing",
      "workarounds": [
        {
          "lang": "en",
          "value": "There is no known mitigation."
        }
      ]
    }
  },
  "cveMetadata": {
    "assignerOrgId": "23aa2041-22e1-471f-9209-9b7396fa234f",
    "assignerShortName": "XEN",
    "cveId": "CVE-2026-79603",
    "datePublished": "2026-09-08T12:11:21.789Z",
    "dateReserved": "2026-08-25T07:35:05.289Z",
    "dateUpdated": "2026-09-08T17:08:33.807Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
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.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.