CVE-2026-89448 (GCVE-0-2026-89448)
Vulnerability from cvelistv5 – Published: 2026-09-11 19:43 – Updated: 2026-10-30 12:31
VLAI
EPSS
VEX
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)
SSVC
Exploitation: none
Automatable: no
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 19:22 UTC
Assigner
References
6 references
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
5d990b627537e59a3a2f039ff588a4750e9c1a6a , < 3fd2b60ea9bd18348f5e971678f31041ef211047
(git)
Affected: 5d990b627537e59a3a2f039ff588a4750e9c1a6a , < 579eb867d3da63f3b5e32f235925e1daa7ec70d0 (git) Affected: 5d990b627537e59a3a2f039ff588a4750e9c1a6a , < aaeb81241e802c86be69394f72d49fde3f861fbb (git) Affected: 5d990b627537e59a3a2f039ff588a4750e9c1a6a , < 45705a6bfdb283f7b3b509010fd617b72f942537 (git) Affected: 5d990b627537e59a3a2f039ff588a4750e9c1a6a , < 87bc611c6c98a41c00feb7b06b0c297dd141a2ae (git) Affected: 5d990b627537e59a3a2f039ff588a4750e9c1a6a , < 607432b2618b61df81134be0ef2562b8300c1216 (git) |
guessed | |
| Linux | Linux |
Affected:
2.6.33
Unaffected: 0 , < 2.6.33 (semver) Unaffected: 6.1.191 , ≤ 6.1.* (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 |
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{
"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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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
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
| Author | Source | Type | Date | Other |
|---|
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.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- 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.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
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.