{"id":"CVE-2026-74439","title":"iommu/vt-d: Clear Present bit before tearing down scalable-mode context entry","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\niommu/vt-d: Clear Present bit before tearing down scalable-mode context entry\n\ndevice_pasid_table_teardown() zeroes the 128-bit scalable-mode context\nentry with context…","severity":"critical","cvss":9.3,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= 81e921fd321614c2ad8ac333b041aae1da7a1c6d < e9e83bcfe37dc719182500dd823c03ab57d934f0","Linux >= 81e921fd321614c2ad8ac333b041aae1da7a1c6d < 588718101e8449605f1c7e858fecb7cfa701cdab","Linux >= 81e921fd321614c2ad8ac333b041aae1da7a1c6d < 7fd4077dc92b91b1b844333c0a06bb9e286db10a","Linux >= 81e921fd321614c2ad8ac333b041aae1da7a1c6d < f46452c3df7a8d8a5addc0926e76ef19ea7da0a0","Linux 333fe86968482ca701c609af590003bcea450e8f","Linux >= 6.8.2 < 6.9","Linux 6.9"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-16T18:56:26.294835Z"},"published":"2026-08-15","updated":"2026-10-16","sourceUpdated":"2026-10-16T19:05:45.325Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-74439","references":[{"url":"https://git.kernel.org/stable/c/e9e83bcfe37dc719182500dd823c03ab57d934f0"},{"url":"https://git.kernel.org/stable/c/588718101e8449605f1c7e858fecb7cfa701cdab"},{"url":"https://git.kernel.org/stable/c/7fd4077dc92b91b1b844333c0a06bb9e286db10a"},{"url":"https://git.kernel.org/stable/c/f46452c3df7a8d8a5addc0926e76ef19ea7da0a0"}],"tags":["cve.org"],"epss":0.00196,"epssPercentile":0.08643,"ingestedAt":"2026-10-16T19:46:24.364Z","slug":"CVE-2026-74439","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\niommu/vt-d: Clear Present bit before tearing down scalable-mode context entry\n\ndevice_pasid_table_teardown() zeroes the 128-bit scalable-mode context\nentry with context_clear_entry() while the Present bit is still set. This\ncreates a window where the hardware can fetch a torn entry, with some\nfields already zeroed while Present is still set, leading to unpredictable\nbehavior or spurious faults. The context-cache invalidation is issued only\nafter the entry has been zeroed, and intel_pasid_free_table() then frees\nthe PASID directory pages, so the IOMMU can keep walking a stale Present=1\nentry that points at freed memory.\n\nWhile x86 provides strong write ordering, the compiler may reorder the two\n64-bit writes to the entry, and the hardware fetch is not guaranteed to be\natomic with respect to multiple CPU writes.\n\nCommit c1e4f1dccbe9d (\"iommu/vt-d: Clear Present bit before tearing down\ncontext entry\") fixed this exact pattern in domain_context_clear_one() and\nthe copied-context path, but device_pasid_table_teardown() was not\nconverted.\n\nAlign it with the \"Guidance to Software for Invalidations\" in the VT-d\nspec, Section 6.5.3.3, using the same ownership handshake as the sibling\nfix: clear only the Present bit, flush it to the IOMMU, perform the\ncontext-cache invalidation, and only then zero the rest of the entry.\n\n## Affected\n\n- `Linux >= 81e921fd321614c2ad8ac333b041aae1da7a1c6d < e9e83bcfe37dc719182500dd823c03ab57d934f0`\n- `Linux >= 81e921fd321614c2ad8ac333b041aae1da7a1c6d < 588718101e8449605f1c7e858fecb7cfa701cdab`\n- `Linux >= 81e921fd321614c2ad8ac333b041aae1da7a1c6d < 7fd4077dc92b91b1b844333c0a06bb9e286db10a`\n- `Linux >= 81e921fd321614c2ad8ac333b041aae1da7a1c6d < f46452c3df7a8d8a5addc0926e76ef19ea7da0a0`\n- `Linux 333fe86968482ca701c609af590003bcea450e8f`\n- `Linux >= 6.8.2 < 6.9`\n- `Linux 6.9`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":51,"depthScoreParts":{"impact":51.2,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}