{"api_version":"1","generated_at":"2026-10-14T19:45:09+00:00","cve":"CVE-2026-79608","urls":{"html":"https://cve.report/CVE-2026-79608","api":"https://cve.report/api/cve/CVE-2026-79608.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-79608","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-79608"},"summary":{"title":"x86/AMD: ineffectual Zenbleed workaround","description":"The workaround for XSA-433 (Zenbleed, CVE-2023-20593) was later\nre-worked to better integrate with other manipulations of the same MSR.\nIn this rework an inverted conditional was introduced, resulting in the\nworkaround to not be applied when needed and vice versa.\n\nFor more details, see:\n  http://xenbits.xen.org/xsa/advisory-433.html","state":"PUBLISHED","assigner":"XEN","published_at":"2026-10-13 16:17:23","updated_at":"2026-10-14 16:10:14"},"problem_types":[],"metrics":[],"references":[{"url":"https://xenbits.xenproject.org/xsa/advisory-515.html","name":"https://xenbits.xenproject.org/xsa/advisory-515.html","refsource":"security@xen.org","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"http://xenbits.xen.org/xsa/advisory-515.html","name":"http://xenbits.xen.org/xsa/advisory-515.html","refsource":"af854a3a-2127-422b-91ae-364da2661108","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-79608","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-79608","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Xen","product":"Xen","version":"unknown consult Xen advisory XSA-515","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[{"source":"CNA","title":"","value":"This issue can be mitigated by disabling AVX, either by booting Xen with\n`cpuid=no-avx` on the command line, or by specifying `cpuid=\"host:avx=0\"` in\nthe vm.cfg file of all untrusted VMs.  However, this will come with a\nsignificant impact on the system and is not recommended for anyone able to\ndeploy the microcode or patch described below.","time":"","lang":"en"}],"exploits":[],"credits":[{"source":"CNA","value":"This issue was discovered by Sashiko + Opus 5.0 and diagnosed as a\nsecurity issue by George Dunlap.","lang":"en"}],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"adp":[{"providerMetadata":{"dateUpdated":"2026-10-13T16:13:41.507Z","orgId":"af854a3a-2127-422b-91ae-364da2661108","shortName":"CVE"},"references":[{"url":"http://xenbits.xen.org/xsa/advisory-515.html"}],"title":"CVE Program Container"}],"cna":{"affected":[{"defaultStatus":"unknown","product":"Xen","vendor":"Xen","versions":[{"status":"unknown","version":"consult Xen advisory XSA-515"}]}],"configurations":[{"lang":"en","value":"Xen versions 4.19.4 and onwards, 4.20.3 and onwards, 4.21.1 and onwards,\nand 4.22 are affected.  Xen versions 4.18, minor versions 4.19.3 and\nearlier, minor versions 4.20.2 and earlier, and 4.21.0 are not affected.\n\nThe vulnerability can only be leveraged on systems running out-of-date\nmicrocode.  Microcode fixing Zenbleed was published in late 2023.\nUpdated firmware subseqeuent to this, or e.g. updated amd-ucode from\nlinux-firmware (for the subset of CPUs covered by linux-firmware) are\nnot vulnerable.\n\nThe original issue and hence the applicability of the workaround is\nspecific to the AMD Zen2 microarchitecture.  AMD do not believe that\nother microarchitectures are affected."}],"credits":[{"lang":"en","type":"finder","value":"This issue was discovered by Sashiko + Opus 5.0 and diagnosed as a\nsecurity issue by George Dunlap."}],"datePublic":"2026-10-13T12:00:00.000Z","descriptions":[{"lang":"en","value":"The workaround for XSA-433 (Zenbleed, CVE-2023-20593) was later\nre-worked to better integrate with other manipulations of the same MSR.\nIn this rework an inverted conditional was introduced, resulting in the\nworkaround to not be applied when needed and vice versa.\n\nFor more details, see:\n  http://xenbits.xen.org/xsa/advisory-433.html"}],"impacts":[{"descriptions":[{"lang":"en","value":"An attacker can exploit this bug to read data from different contexts on\nthe same core.  Examples of such data includes key material, cypher and\nplaintext from the AES-NI instructions, or the contents of REP-MOVS\ninstructions, commonly used to implement memcpy()."}]}],"providerMetadata":{"dateUpdated":"2026-10-13T15:44:08.729Z","orgId":"23aa2041-22e1-471f-9209-9b7396fa234f","shortName":"XEN"},"references":[{"url":"https://xenbits.xenproject.org/xsa/advisory-515.html"}],"title":"x86/AMD: ineffectual Zenbleed workaround","workarounds":[{"lang":"en","value":"This issue can be mitigated by disabling AVX, either by booting Xen with\n`cpuid=no-avx` on the command line, or by specifying `cpuid=\"host:avx=0\"` in\nthe vm.cfg file of all untrusted VMs.  However, this will come with a\nsignificant impact on the system and is not recommended for anyone able to\ndeploy the microcode or patch described below."}]}},"cveMetadata":{"assignerOrgId":"23aa2041-22e1-471f-9209-9b7396fa234f","assignerShortName":"XEN","cveId":"CVE-2026-79608","datePublished":"2026-10-13T15:44:08.729Z","dateReserved":"2026-08-25T07:35:05.289Z","dateUpdated":"2026-10-13T16:13:41.507Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-10-13 16:17:23","lastModifiedDate":"2026-10-14 16:10:14","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"79608","Ordinal":"1","Title":"x86/AMD: ineffectual Zenbleed workaround","CVE":"CVE-2026-79608","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"79608","Ordinal":"1","NoteData":"The workaround for XSA-433 (Zenbleed, CVE-2023-20593) was later\nre-worked to better integrate with other manipulations of the same MSR.\nIn this rework an inverted conditional was introduced, resulting in the\nworkaround to not be applied when needed and vice versa.\n\nFor more details, see:\n  http://xenbits.xen.org/xsa/advisory-433.html","Type":"Description","Title":"x86/AMD: ineffectual Zenbleed workaround"}]}}}