{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-79611", "assignerOrgId": "23aa2041-22e1-471f-9209-9b7396fa234f", "state": "PUBLISHED", "assignerShortName": "XEN", "dateReserved": "2026-08-25T07:35:05.290Z", "datePublished": "2026-10-13T15:44:56.361Z", "dateUpdated": "2026-10-20T17:31:41.971Z"}, "containers": {"cna": {"title": "VMX: VMentry failure with branch tracing and blocked states", "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."}]}], "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."}], "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."}], "credits": [{"lang": "en", "type": "finder", "value": "This issue was discovered by Claude Opus and diagnosed as a security issue\nby Teddy Astie of Vates."}], "references": [{"url": "https://xenbits.xenproject.org/xsa/advisory-518.html"}], "providerMetadata": {"orgId": "23aa2041-22e1-471f-9209-9b7396fa234f", "shortName": "XEN", "dateUpdated": "2026-10-13T15:44:56.361Z"}}, "adp": [{"title": "CVE Program Container", "references": [{"url": "http://xenbits.xen.org/xsa/advisory-518.html"}, {"url": "http://www.openwall.com/lists/oss-security/2026/10/13/7"}], "providerMetadata": {"orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2026-10-13T16:13:51.786Z"}}, {"problemTypes": [{"descriptions": [{"type": "CWE", "cweId": "CWE-843", "lang": "en", "description": "CWE-843 Access of Resource Using Incompatible Type ('Type Confusion')"}]}], "metrics": [{"cvssV3_1": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 5.5, "attackVector": "LOCAL", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "NONE"}}, {"other": {"type": "ssvc", "content": {"timestamp": "2026-10-20T17:31:36.841344Z", "id": "CVE-2026-79611", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-20T17:31:41.971Z"}}]}}

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{"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": "2026-10-20T18:17:22.447", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 5.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 3.6, "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-79611", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-10-20T17:31:36.841344Z", "version": "2.0.3"}}]}, "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", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-843"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}

{}