{"id":"CVE-2026-79609","title":"XPTI (Xen Page Table Isolation) was introduced to mitigate Meltdown\n(CVE-2017-5754, one aspect of XSA-254)","summary":"XPTI (Xen Page Table Isolation) was introduced to mitigate Meltdown\n(CVE-2017-5754, one aspect of XSA-254).  This involves copying 64-bit PV\nguest page table entries from guest-chosen root page tables to the Xen-\nchosen one which is in a…","severity":"high","published":"2026-10-13","updated":"2026-10-14","sourceUpdated":"2026-10-14T16:10:14.750","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-79609","references":[{"url":"https://xenbits.xenproject.org/xsa/advisory-516.html","label":"security@xen.org"},{"url":"http://xenbits.xen.org/xsa/advisory-516.html","label":"af854a3a-2127-422b-91ae-364da2661108"}],"tags":["nvd","cve.org"],"ingestedAt":"2026-10-13T16:35:46.745Z","vendor":"Xen","product":"Xen","affected":["Xen"],"epss":0.00106,"epssPercentile":0.01104,"cvss":8.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-20T17:34:35.122730Z"},"cvssSource":"adp","slug":"CVE-2026-79609","body":"## Overview\n\nXPTI (Xen Page Table Isolation) was introduced to mitigate Meltdown\n(CVE-2017-5754, one aspect of XSA-254).  This involves copying 64-bit PV\nguest page table entries from guest-chosen root page tables to the Xen-\nchosen one which is in actual use by hardware.  To read the guest root\npage table, the directmap is used.  PV guests, however, have a directmap\nwhich may not cover all memory; in particular this is the case if any\nmemory extends beyond the 5 TiB (CONFIG_BIGMEM=y: 3.5 TiB) address\nboundary.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":48,"depthScoreParts":{"impact":48.4,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":226050,"id":"CVE-2026-79609","ts":1792520125430,"field":"cvss","old":null,"new":"8.8"},{"seq":226049,"id":"CVE-2026-79609","ts":1792520125430,"field":"severity","old":"none","new":"high"}]}