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

Vulnerability from cvelistv5 – Published: 2026-10-13 15:44 – Updated: 2026-10-13 16:13
VLAI
Title
VMX: VMentry failure with branch tracing and blocked states
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.
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
Impacted products
Vendor Product Version CPE status
Xen Xen Unknown: consult Xen advisory XSA-518
guessed Create a notification for this product.
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
To clipboard 

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            "url": "http://www.openwall.com/lists/oss-security/2026/10/13/7"
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          "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": [
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          "type": "finder",
          "value": "This issue was discovered by Claude Opus and diagnosed as a security issue\nby Teddy Astie of Vates."
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      "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": [
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              "value": "HVM/PVH guest userspace code may be able to crash the guest, resulting\nin a guest Denial of Service."
            }
          ]
        }
      ],
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        "dateUpdated": "2026-10-13T15:44:56.361Z",
        "orgId": "23aa2041-22e1-471f-9209-9b7396fa234f",
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          "url": "https://xenbits.xenproject.org/xsa/advisory-518.html"
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      "title": "VMX: VMentry failure with branch tracing and blocked states",
      "workarounds": [
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          "value": "Running only PV guests will avoid this vulnerability.\n\nRunning HVM guests on only AMD or Hygon hardware will also avoid this\nvulnerability."
        }
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    "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",
  "vulnerability-lookup:meta": {
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      "date": "2026-10-14",
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          }
        ],
        "id": "CVE-2026-79611",
        "lastModified": "2026-10-14T16:10:14.750",
        "metrics": {},
        "published": "2026-10-13T16:17:23.347",
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        "sourceIdentifier": "security@xen.org",
        "vulnStatus": "Awaiting Analysis"
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