{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-74439", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-15T05:44:03.897Z", "datePublished": "2026-08-15T05:59:36.655Z", "dateUpdated": "2026-08-17T05:47:13.219Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T05:47:13.219Z" }, "descriptions": [ { "lang": "en", "value": "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." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H", "baseScore": 9.3, "baseSeverity": "CRITICAL" }, "scenarios": [ { "lang": "en", "value": "AV:L - The flaw is in Intel VT-d scalable-mode PASID context teardown reached only via local kernel IOMMU device-release paths (intel_iommu_release_device → device_pasid_table_teardown), triggered by PCI hot-unplug, sysfs driver unbind, or iommu deinit—not by any network-facing protocol.\nAC:L - This is a use-after-free where intel_pasid_free_table() frees PASID directory pages while the IOMMU may still cache a Present=1 context entry; an attacker controlling a PASID-capable device can keep DMA active and time bus removal/teardown to hit the stale-entry window reliably (AC:L per UAF guidance).\nPR:N - A malicious PASID-capable PCIe device can trigger the vulnerable intel_iommu_release_device teardown by physical hot-unplug (pci_stop_and_remove_bus_device) while sustaining DMA, requiring no authenticated host account or capability on the target system.\nUI:N - No victim interaction is required beyond the attacker's own device removal or driver-unbind orchestration; the vulnerable teardown executes automatically once the PCI/IOMMU release path runs.\nS:C - A stale or torn scalable-mode context entry breaks VT-d DMA isolation—the IOMMU can translate device DMA against freed PASID table memory, crossing the device/host (or guest/host) IOMMU security boundary per kernel IOMMU bypass guidance.\nC:H - With the IOMMU walking freed PASID directory pages, a controlled device can DMA-read host physical memory outside its assigned domain, yielding arbitrary cross-boundary read disclosure (C:H; UAF enables attacker influence over translation contents).\nI:H - The same mistranslation gives the device an arbitrary DMA write primitive against host memory outside its domain, enabling data modification and potential control-flow hijack via memory corruption (standard UAF/IOMMU-bypass I:H guidance).\nA:H - The commit documents unpredictable behavior and spurious DMAR faults from torn Present entries; freed PASID tables under active IOMMU walks can fault-storm, hang, or panic the host—any kernel crash/UAF qualifies as A:H." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/iommu/intel/pasid.c" ], "versions": [ { "version": "81e921fd321614c2ad8ac333b041aae1da7a1c6d", "lessThan": "e9e83bcfe37dc719182500dd823c03ab57d934f0", "status": "affected", "versionType": "git" }, { "version": "81e921fd321614c2ad8ac333b041aae1da7a1c6d", "lessThan": "588718101e8449605f1c7e858fecb7cfa701cdab", "status": "affected", "versionType": "git" }, { "version": "81e921fd321614c2ad8ac333b041aae1da7a1c6d", "lessThan": "7fd4077dc92b91b1b844333c0a06bb9e286db10a", "status": "affected", "versionType": "git" }, { "version": "81e921fd321614c2ad8ac333b041aae1da7a1c6d", "lessThan": "f46452c3df7a8d8a5addc0926e76ef19ea7da0a0", "status": "affected", "versionType": "git" }, { "version": "333fe86968482ca701c609af590003bcea450e8f", "status": "affected", "versionType": "git" }, { "version": "6.8.2", "lessThan": "6.9", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/iommu/intel/pasid.c" ], "versions": [ { "version": "6.9", "status": "affected" }, { "version": "0", "lessThan": "6.9", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.97", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.40", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.5", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.9", "versionEndExcluding": "6.12.97" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.9", "versionEndExcluding": "6.18.40" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.9", "versionEndExcluding": "7.1.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.9", "versionEndExcluding": "7.2" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.8.2" } ] } ] } ], "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" } ], "title": "iommu/vt-d: Clear Present bit before tearing down scalable-mode context entry", "x_generator": { "engine": "bippy-1.2.0" } } } }