Vulnerability-Lookup

FKIE_CVE-2026-79611

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

Severity

Summary

For XSA-308 logic was introduced, as VMX VMEntry checks do not like the exact combination of state which occurs when #DB in intercepted, Single Stepping is active, and blocked by STI/MovSS is active, despite this being a legitimate state to be in. The resulting VMEntry failure is fatal to the guest. Sadly there is another special sub-case of the above, with branch tracing enabled. In that case the prior adjustment would still cause a VMentry failure, as before fatal to the guest.

References

	URL	Tags
	security@xen.org	https://xenbits.xenproject.org/xsa/advisory-518.html
	af854a3a-2127-422b-91ae-364da2661108	http://www.openwall.com/lists/oss-security/2026/10/13/7
	af854a3a-2127-422b-91ae-364da2661108	http://xenbits.xen.org/xsa/advisory-518.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-518"
            }
          ]
        }
      ],
      "source": "security@xen.org"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "For XSA-308 logic was introduced, as VMX VMEntry checks do not like the\nexact combination of state which occurs when #DB in intercepted, Single\nStepping is active, and blocked by STI/MovSS is active, despite this being\na legitimate state to be in.  The resulting VMEntry failure is fatal to\nthe guest.\n\nSadly there is another special sub-case of the above, with branch tracing\nenabled.  In that case the prior adjustment would still cause a VMentry\nfailure, as before fatal to the guest."
    }
  ],
  "id": "CVE-2026-79611",
  "lastModified": "2026-10-14T16:10:14.750",
  "metrics": {},
  "published": "2026-10-13T16:17:23.347",
  "references": [
    {
      "source": "security@xen.org",
      "url": "https://xenbits.xenproject.org/xsa/advisory-518.html"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "http://www.openwall.com/lists/oss-security/2026/10/13/7"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "http://xenbits.xen.org/xsa/advisory-518.html"
    }
  ],
  "sourceIdentifier": "security@xen.org",
  "vulnStatus": "Awaiting Analysis"
}

CVE-2026-79611 (GCVE-0-2026-79611)

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

Title

VMX: VMentry failure with branch tracing and blocked states

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

3 references

URL	Tags
https://xenbits.xenproject.org/xsa/advisory-518.html
http://xenbits.xen.org/xsa/advisory-518.html
http://www.openwall.com/lists/oss-security/2026/10/13/7

Impacted products

1 product

Vendor	Product	Version
Xen	Xen	Unknown: consult Xen advisory XSA-518

Date Public

2026-10-13 12:00

Credits

This issue was discovered by Claude Opus and diagnosed as a security issue by Teddy Astie of Vates.

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "providerMetadata": {
          "dateUpdated": "2026-10-13T16:13:51.786Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "url": "http://xenbits.xen.org/xsa/advisory-518.html"
          },
          {
            "url": "http://www.openwall.com/lists/oss-security/2026/10/13/7"
          }
        ],
        "title": "CVE Program Container"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unknown",
          "product": "Xen",
          "vendor": "Xen",
          "versions": [
            {
              "status": "unknown",
              "version": "consult Xen advisory XSA-518"
            }
          ]
        }
      ],
      "configurations": [
        {
          "lang": "en",
          "value": "All versions of Xen are affected.\n\nOnly systems supporting VMX hardware virtual extensions (Intel, VIA or\nZhaoxin CPUs) are affected.  Arm as well as AMD and Hygon systems are\nunaffected.\n\nOnly HVM/PVH guests are affected.  PV guests cannot leverage the\nvulnerability."
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "This issue was discovered by Claude Opus and diagnosed as a security issue\nby Teddy Astie of Vates."
        }
      ],
      "datePublic": "2026-10-13T12:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "For XSA-308 logic was introduced, as VMX VMEntry checks do not like the\nexact combination of state which occurs when #DB in intercepted, Single\nStepping is active, and blocked by STI/MovSS is active, despite this being\na legitimate state to be in.  The resulting VMEntry failure is fatal to\nthe guest.\n\nSadly there is another special sub-case of the above, with branch tracing\nenabled.  In that case the prior adjustment would still cause a VMentry\nfailure, as before fatal to the guest."
        }
      ],
      "impacts": [
        {
          "descriptions": [
            {
              "lang": "en",
              "value": "HVM/PVH guest userspace code may be able to crash the guest, resulting\nin a guest Denial of Service."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-13T15:44:56.361Z",
        "orgId": "23aa2041-22e1-471f-9209-9b7396fa234f",
        "shortName": "XEN"
      },
      "references": [
        {
          "url": "https://xenbits.xenproject.org/xsa/advisory-518.html"
        }
      ],
      "title": "VMX: VMentry failure with branch tracing and blocked states",
      "workarounds": [
        {
          "lang": "en",
          "value": "Running only PV guests will avoid this vulnerability.\n\nRunning HVM guests on only AMD or Hygon hardware will also avoid this\nvulnerability."
        }
      ]
    }
  },
  "cveMetadata": {
    "assignerOrgId": "23aa2041-22e1-471f-9209-9b7396fa234f",
    "assignerShortName": "XEN",
    "cveId": "CVE-2026-79611",
    "datePublished": "2026-10-13T15:44:56.361Z",
    "dateReserved": "2026-08-25T07:35:05.290Z",
    "dateUpdated": "2026-10-13T16:13:51.786Z",
    "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.

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