{"id":"CVE-2026-74439","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-74439","summary":"iommu/vt-d: Clear Present bit before tearing down scalable-mode context entry","details":"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_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.","published":"2026-08-15T05:59:36.655Z","modified":"2026-08-18T03:56:48.035558023Z","cvss":{"score":9.3,"severity":"CRITICAL","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Linux","name":"Kernel","fixedVersion":"6.12.97"}],"fix":null,"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/588718101e8449605f1c7e858fecb7cfa701cdab"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7fd4077dc92b91b1b844333c0a06bb9e286db10a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e9e83bcfe37dc719182500dd823c03ab57d934f0"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f46452c3df7a8d8a5addc0926e76ef19ea7da0a0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74439.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-74439"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-18T03:56:48.035558023Z"}}