Vulnerability-Lookup

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

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.

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	CPE status
Xen	Xen	Unknown: consult Xen advisory XSA-511	guessed

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",
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        "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"
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        "metrics": [
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              "attackComplexity": "LOW",
              "attackVector": "NETWORK",
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              "baseSeverity": "MEDIUM",
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              "userInteraction": "NONE",
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            }
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                "options": [
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                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-08T13:42:37.092287Z",
                "version": "2.0.3"
              },
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            }
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        ],
        "problemTypes": [
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                "type": "CWE"
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          "dateUpdated": "2026-09-08T13:42:41.424Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
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      }
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          "vendor": "Xen",
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            }
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      ],
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          "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": [
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          "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",
  "vulnerability-lookup:meta": {
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      "date": "2026-09-09",
      "epss": "0.00231",
      "percentile": "0.13913"
    },
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    "redhat_vex": {
      "current_release_date": "2026-09-08T17:33:14+00:00",
      "cve": "CVE-2026-79603",
      "id": "CVE-2026-79603",
      "initial_release_date": "2026-09-08T12:11:21.789000+00:00",
      "product_status:known_not_affected": "1",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "xen: Xen: PV guests can modify scrubbed memory pages due to stale TLB entries",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-79603.json",
      "version": "3"
    },
    "vulnrichment": {
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}

FKIE_CVE-2026-79603

Vulnerability from fkie_nvd - Published: 2026-09-08 13:17 - Updated: 2026-09-08 19:20

Severity

4.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Summary

References

	URL	Tags
	security@xen.org	https://xenbits.xenproject.org/xsa/advisory-511.html
	af854a3a-2127-422b-91ae-364da2661108	http://www.openwall.com/lists/oss-security/2026/09/08/8
	af854a3a-2127-422b-91ae-364da2661108	http://xenbits.xen.org/xsa/advisory-511.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-511"
            }
          ]
        }
      ],
      "source": "security@xen.org"
    }
  ],
  "cveTags": [],
  "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."
    }
  ],
  "id": "CVE-2026-79603",
  "lastModified": "2026-09-08T19:20:25.117",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "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"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 1.4,
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-79603",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-09-08T13:42:37.092287Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-09-08T13:17:27.253",
  "references": [
    {
      "source": "security@xen.org",
      "url": "https://xenbits.xenproject.org/xsa/advisory-511.html"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "http://www.openwall.com/lists/oss-security/2026/09/08/8"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "http://xenbits.xen.org/xsa/advisory-511.html"
    }
  ],
  "sourceIdentifier": "security@xen.org",
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-664"
        }
      ],
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "type": "Secondary"
    }
  ]
}

GHSA-PWV5-R8HR-FVGR

Vulnerability from github – Published: 2026-09-08 15:31 – Updated: 2026-09-08 18:31

Details

Severity

4.3 (Medium)


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

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-79603"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-664"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-08T13:17:27Z",
    "severity": "MODERATE"
  },
  "details": "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.",
  "id": "GHSA-pwv5-r8hr-fvgr",
  "modified": "2026-09-08T18:31:48Z",
  "published": "2026-09-08T15:31:54Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-79603"
    },
    {
      "type": "WEB",
      "url": "https://xenbits.xenproject.org/xsa/advisory-511.html"
    },
    {
      "type": "WEB",
      "url": "http://www.openwall.com/lists/oss-security/2026/09/08/8"
    },
    {
      "type": "WEB",
      "url": "http://xenbits.xen.org/xsa/advisory-511.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N",
      "type": "CVSS_V3"
    }
  ]
}

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.

Action not permitted

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

FKIE_CVE-2026-79603

GHSA-PWV5-R8HR-FVGR

Tags

Sightings

Nomenclature