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

Vulnerability from cvelistv5 – Published: 2026-09-11 19:43 – Updated: 2026-10-19 08:46
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
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 19:22 UTC
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 7061 records in the last 180 days details
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 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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                  "version": "5d990b627537e59a3a2f039ff588a4750e9c1a6a",
                  "versionType": "git"
                },
                {
                  "lessThan": "607432b2618b61df81134be0ef2562b8300c1216",
                  "status": "affected",
                  "version": "5d990b627537e59a3a2f039ff588a4750e9c1a6a",
                  "versionType": "git"
                }
              ]
            },
            {
              "defaultStatus": "affected",
              "product": "Linux",
              "programFiles": [
                "drivers/iommu/intel/dmar.c",
                "drivers/iommu/intel/iommu.c",
                "drivers/iommu/intel/iommu.h"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "status": "affected",
                  "version": "2.6.33"
                },
                {
                  "lessThan": "2.6.33",
                  "status": "unaffected",
                  "version": "0",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.6.*",
                  "status": "unaffected",
                  "version": "6.6.157",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.12.*",
                  "status": "unaffected",
                  "version": "6.12.109",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.18.*",
                  "status": "unaffected",
                  "version": "6.18.50",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "7.2.*",
                  "status": "unaffected",
                  "version": "7.2.4",
                  "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": "6.6.157",
                      "versionStartIncluding": "2.6.33",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.12.109",
                      "versionStartIncluding": "2.6.33",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.18.50",
                      "versionStartIncluding": "2.6.33",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "7.2.4",
                      "versionStartIncluding": "2.6.33",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "7.3",
                      "versionStartIncluding": "2.6.33",
                      "vulnerable": true
                    }
                  ],
                  "negate": false,
                  "operator": "OR"
                }
              ]
            }
          ],
          "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": "2026-10-19T08:46:57.768Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "shortName": "Linux"
          },
          "references": [
            {
              "url": "https://git.kernel.org/stable/c/579eb867d3da63f3b5e32f235925e1daa7ec70d0"
            },
            {
              "url": "https://git.kernel.org/stable/c/aaeb81241e802c86be69394f72d49fde3f861fbb"
            },
            {
              "url": "https://git.kernel.org/stable/c/45705a6bfdb283f7b3b509010fd617b72f942537"
            },
            {
              "url": "https://git.kernel.org/stable/c/87bc611c6c98a41c00feb7b06b0c297dd141a2ae"
            },
            {
              "url": "https://git.kernel.org/stable/c/607432b2618b61df81134be0ef2562b8300c1216"
            }
          ],
          "title": "iommu/vt-d: Force requesting ACS when tboot is enabled",
          "x_generator": {
            "engine": "bippy-1.2.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2026-89448",
        "datePublished": "2026-09-11T19:43:14.746Z",
        "dateReserved": "2026-09-11T19:38:34.706Z",
        "dateUpdated": "2026-10-19T08:46:57.768Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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