CVE-2026-89448 (GCVE-0-2026-89448)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:43 – Updated: 2026-09-14 11:59
VLAI
Title
iommu/vt-d: Force requesting ACS when tboot is enabled
Summary
In the Linux kernel, the following vulnerability has been resolved: iommu/vt-d: Force requesting ACS when tboot is enabled Currently the conditions of requesting ACS in detect_intel_iommu() don't include tboot, leading to a possible misconfiguration with ACS disabled (e.g. due to user opts) while iommu is later forced on by tboot_force_iommu(). Fix it by checking tboot in detect_intel_iommu().
Severity
9.3 (Critical)
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 5d990b627537e59a3a2f039ff588a4750e9c1a6a , < 579eb867d3da63f3b5e32f235925e1daa7ec70d0 (git)
Affected: 5d990b627537e59a3a2f039ff588a4750e9c1a6a , < aaeb81241e802c86be69394f72d49fde3f861fbb (git)
Affected: 5d990b627537e59a3a2f039ff588a4750e9c1a6a , < 45705a6bfdb283f7b3b509010fd617b72f942537 (git)
Affected: 5d990b627537e59a3a2f039ff588a4750e9c1a6a , < 87bc611c6c98a41c00feb7b06b0c297dd141a2ae (git)
Affected: 5d990b627537e59a3a2f039ff588a4750e9c1a6a , < 607432b2618b61df81134be0ef2562b8300c1216 (git)
guessed Create a notification for this product.
Linux Linux Affected: 2.6.33
Unaffected: 0 , < 2.6.33 (semver)
Unaffected: 6.6.157 , ≤ 6.6.* (semver)
Unaffected: 6.12.109 , ≤ 6.12.* (semver)
Unaffected: 6.18.50 , ≤ 6.18.* (semver)
Unaffected: 7.2.4 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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{
  "containers": {
    "cna": {
      "affected": [
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          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/iommu/intel/dmar.c",
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              "status": "unaffected",
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              "versionType": "semver"
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              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
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              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
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        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "vulnerable": true
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                  "versionEndExcluding": "7.3-rc1",
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                  "vulnerable": true
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\niommu/vt-d: Force requesting ACS when tboot is enabled\n\nCurrently the conditions of requesting ACS in detect_intel_iommu()\ndon\u0027t include tboot, leading to a possible misconfiguration with ACS\ndisabled (e.g. due to user opts) while iommu is later forced on by\ntboot_force_iommu().\n\nFix it by checking tboot in detect_intel_iommu()."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.3,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - detect_intel_iommu() runs at boot from pci_iommu_alloc() and, when tboot later forces VT-d on, skips pci_request_acs(); a local PCIe/Thunderbolt DMA device or VFIO-passthrough guest can then spoof requester IDs and issue peer-to-peer DMA. This is not a network-protocol path.\nAC:L - On a tboot launch where intel_iommu=off, iommu=off, or default dmar_disabled skipped pci_request_acs(), ACS SV/RR/CR/UF/TB are never programmed; an attacker-controlled device can then deterministically perform P2P DMA or RID spoofing with no race or layout luck.\nPR:N - A malicious PCIe/Thunderbolt device or a tenant with an assigned passthrough/SR-IOV function issues the DMA itself and needs no host account, capability, or init-namespace root, matching other VT-d isolation-bypass scores for unauthenticated devices.\nUI:N - After the kernel boots with tboot-forced VT-d and ACS still disabled, the attacker\u2019s device performs DMA on its own; no separate victim action such as mounting a filesystem or opening a file is required.\nS:C - Missing ACS lets a device spoof requester IDs and send peer-to-peer TLPs that never reach the IOMMU, crossing the device/host DMA isolation boundary that tboot forces VT-d on to enforce (IOMMU/DMA boundary bypass is Scope Changed).\nC:H - Without ACS source validation, request redirect, and translation blocking, a device can impersonate another requester ID or DMA to peer BARs, reading host or peer-device memory outside its IOMMU domain (arbitrary DMA disclosure).\nI:H - The same ACS gap yields DMA writes into host or peer-device memory, including ATS without translation blocking on external/untrusted ports, providing an arbitrary write primitive that can corrupt kernel memory and hijack control flow.\nA:H - Unchecked DMA writes and IOMMU-bypassing P2P traffic can corrupt kernel structures or provoke DMAR faults, oopses, and panics; any such host crash qualifies as High availability impact."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-14T11:59:55.683Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/579eb867d3da63f3b5e32f235925e1daa7ec70d0"
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          "url": "https://git.kernel.org/stable/c/aaeb81241e802c86be69394f72d49fde3f861fbb"
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        },
        {
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        },
        {
          "url": "https://git.kernel.org/stable/c/607432b2618b61df81134be0ef2562b8300c1216"
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      "title": "iommu/vt-d: Force requesting ACS when tboot is enabled",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89448",
    "datePublished": "2026-09-11T19:43:14.746Z",
    "dateReserved": "2026-09-11T19:38:34.706Z",
    "dateUpdated": "2026-09-14T11:59:55.683Z",
    "state": "PUBLISHED"
  },
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      "date": "2026-09-23",
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      "percentile": "0.0402"
    },
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      "id": "msrc_CVE-2026-89448",
      "initial_release_date": "2026-09-13T01:10:43.000Z",
      "product_status:known_affected": "2",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "iommu/vt-d: Force requesting ACS when tboot is enabled",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-89448.json",
      "version": "3"
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    "nvd": {
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                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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        "cveTags": [],
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          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\niommu/vt-d: Force requesting ACS when tboot is enabled\n\nCurrently the conditions of requesting ACS in detect_intel_iommu()\ndon\u0027t include tboot, leading to a possible misconfiguration with ACS\ndisabled (e.g. due to user opts) while iommu is later forced on by\ntboot_force_iommu().\n\nFix it by checking tboot in detect_intel_iommu()."
          }
        ],
        "id": "CVE-2026-89448",
        "lastModified": "2026-09-14T13:19:01.800",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 9.3,
                "baseSeverity": "CRITICAL",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "CHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H",
                "version": "3.1"
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              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
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        "published": "2026-09-11T20:19:25.347",
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
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    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-09-18T19:54:55+00:00",
      "cve": "CVE-2026-89448",
      "id": "CVE-2026-89448",
      "initial_release_date": "2026-09-11T00:00:00+00:00",
      "product_status:known_affected": "234",
      "product_status:known_not_affected": "42",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: iommu/vt-d: Force requesting ACS when tboot is enabled",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89448.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-21T16:38:02Z",
      "cve": "CVE-2026-89448",
      "id": "CVE-2026-89448",
      "initial_release_date": "2026-09-12T16:28:16Z",
      "product_status:known_affected": "353",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-89448",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-89448.json",
      "version": "5"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.