CVE-2026-90243 (GCVE-0-2026-90243)
Vulnerability from cvelistv5
Published
2026-09-17 16:07
Modified
2026-10-19 09:00
Severity ?
8.1 (High) - CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: iommu/vt-d: Clear Present bit before tearing down copied context entry copied_context_tear_down() zeroes the 128-bit context entry with context_clear_entry() while the Present bit is still set, and only then issues the context-cache and IOTLB invalidations. This leaves a window in which hardware can fetch a torn entry, with some fields already zeroed while Present is still set, leading to unpredictable behaviour or spurious faults. While x86 provides strong write ordering, the compiler may reorder the writes to the two 64-bit halves of the entry, and the hardware fetch is not guaranteed to be atomic with respect to multiple CPU writes. There is no cacheline flush before the invalidation either, so on an IOMMU without coherent access to the context table the zeroed entry may not be visible to hardware at the point the invalidation is submitted. Apply the same ownership handshake described in the VT-d spec, Section 6.5.3.3 ("Guidance to Software for Invalidations"): clear only the Present bit, flush it out to the IOMMU, perform the invalidations, and only then zero the remainder of the entry.
References
Impacted products
Vendor Product Version
Linux Linux Version: c7191984e5aade540f1a3845a116537c89572655
Version: c7191984e5aade540f1a3845a116537c89572655
Version: c7191984e5aade540f1a3845a116537c89572655
Version: c7191984e5aade540f1a3845a116537c89572655
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/iommu/intel/iommu.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/iommu/intel/iommu.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.12"
            },
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              "lessThan": "6.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.110",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.52",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.110",
                  "versionStartIncluding": "6.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.52",
                  "versionStartIncluding": "6.12",
                  "vulnerable": true
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                  "vulnerable": true
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                {
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                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "6.12",
                  "vulnerable": true
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\niommu/vt-d: Clear Present bit before tearing down copied context entry\n\ncopied_context_tear_down() zeroes the 128-bit context entry with\ncontext_clear_entry() while the Present bit is still set, and only then\nissues the context-cache and IOTLB invalidations.  This leaves a window\nin which hardware can fetch a torn entry, with some fields already zeroed\nwhile Present is still set, leading to unpredictable behaviour or\nspurious faults.  While x86 provides strong write ordering, the compiler\nmay reorder the writes to the two 64-bit halves of the entry, and the\nhardware fetch is not guaranteed to be atomic with respect to multiple\nCPU writes.\n\nThere is no cacheline flush before the invalidation either, so on an\nIOMMU without coherent access to the context table the zeroed entry may\nnot be visible to hardware at the point the invalidation is submitted.\n\nApply the same ownership handshake described in the VT-d spec, Section\n6.5.3.3 (\"Guidance to Software for Invalidations\"): clear only the Present\nbit, flush it out to the IOMMU, perform the invalidations, and only then\nzero the remainder of the entry."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.1,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - copied_context_tear_down() runs only from domain_context_mapping_one() and context_setup_pass_through() on crash-kernel attach (__iommu_probe_device \u2192 iommu_setup_default_domain \u2192 intel_iommu_attach_device or identity_domain_attach_dev). The trigger is in-flight PCIe DMA against a copied VT-d context, not a network protocol message.\nAC:H - context_clear_entry() does two unordered 64-bit stores (context-\u003elo=0, context-\u003ehi=0) while Present is still set, then flush_context/flush_iotlb. Hitting a torn Present=1 fetch depends on compiler store order, a non-atomic IOMMU 128-bit read, and/or a non-coherent IOMMU seeing unflushed writes\u2014timing the attacker cannot reliably force.\nPR:N - copy_translation_tables() in init_dmars() sets copied_tables only when is_kdump_kernel() and translation_pre_enabled(); copied_context_tear_down() then runs from __iommu_probe_device() with no capable() check. A DMA-capable PCIe device with leftover in-flight DMA needs no host account.\nUI:N - Crash-kernel PCI/IOMMU probing calls iommu_setup_default_domain() and then copied_context_tear_down() before the device driver probe/reset; no victim must mount a filesystem, open a file, or otherwise cooperate.\nS:C - A torn Present=1 copied context (old lo with ASR/TT intact, hi already zeroed so DID=0 and AW=0) lets VT-d translate that device\u2019s DMA through the wrong domain-id and address-width against the copied page-table root, crossing the IOMMU DMA isolation boundary.\nC:H - Hardware walking that torn copied context can map in-flight DMA reads to host physical pages outside the device\u2019s intended domain, including crash-kernel memory beside the old tables copied by copy_translation_tables(), yielding cross-domain disclosure.\nI:H - The same Present=1 / DID=0 / AW=0 mix with the leftover ASR from the copied entry lets the device DMA-write host memory outside its assigned domain, an arbitrary write across the VT-d isolation boundary.\nA:H - The fix documents unpredictable VT-d behaviour and spurious faults when hardware fetches the torn copied context in copied_context_tear_down(); those DMAR faults can oops, panic, or abort the crash dump."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:00:19.209Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/97750a8dce79c1a9b2b2d2a020b61b800141996c"
        },
        {
          "url": "https://git.kernel.org/stable/c/3c88cfedc7768b1ae2dc7ddc71547ae9a1aaff7d"
        },
        {
          "url": "https://git.kernel.org/stable/c/6b822d18c33af9d1e16a8e5e6aa6e656987b09de"
        },
        {
          "url": "https://git.kernel.org/stable/c/f532c57985b1a7d6b7e37e05506b46d413e5cca4"
        }
      ],
      "title": "iommu/vt-d: Clear Present bit before tearing down copied context entry",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90243",
    "datePublished": "2026-09-17T16:07:46.488Z",
    "dateReserved": "2026-09-11T19:38:34.795Z",
    "dateUpdated": "2026-10-19T09:00:19.209Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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