{"id":"CVE-2026-79611","state":"PUBLISHED","title":"VMX: VMentry failure with branch tracing and blocked states","description":"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.","publishedAt":"2026-10-13T15:44:56.361Z","updatedAt":"2026-10-20T17:31:41.971Z","severity":{"score":5.5,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","source":"CISA-ADP"},"assigner":"XEN","products":["Xen Xen"],"affected":[{"vendor":"Xen","product":"Xen","defaultStatus":"unknown","versions":[{"version":"consult Xen advisory XSA-518","status":"unknown"}]}],"references":["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"],"weaknesses":["CWE-843"],"ingestedAt":"2026-10-29T20:13:07.220Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/79xxx/CVE-2026-79611.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-79611","state":"PUBLISHED","datePublished":"2026-10-13T15:44:56.361Z","dateUpdated":"2026-10-20T17:31:41.971Z","assignerShortName":"XEN","assignerOrgId":"23aa2041-22e1-471f-9209-9b7396fa234f","dateReserved":"2026-08-25T07:35:05.290Z"},"containers":{"cna":{"title":"VMX: VMentry failure with branch tracing and blocked states","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."}],"affected":[{"vendor":"Xen","product":"Xen","defaultStatus":"unknown","versions":[{"version":"consult Xen advisory XSA-518","status":"unknown"}]}],"references":[{"url":"https://xenbits.xenproject.org/xsa/advisory-518.html"}],"providerMetadata":{"shortName":"XEN","orgId":"23aa2041-22e1-471f-9209-9b7396fa234f","dateUpdated":"2026-10-13T15:44:56.361Z"},"datePublic":"2026-10-13T12:00:00.000Z","impacts":[{"descriptions":[{"lang":"en","value":"HVM/PVH guest userspace code may be able to crash the guest, resulting\nin a guest Denial of Service."}]}],"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."}]},"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":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2026-10-13T16:13:51.786Z"}},{"title":"CISA ADP Vulnrichment","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"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-843","type":"CWE","lang":"en","description":"CWE-843 Access of Resource Using Incompatible Type ('Type Confusion')"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-20T17:31:41.971Z"}}]}}}