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Response snapshot Oct 30, 2026, 17:01 UTC

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VulnerabilityCVE-2026-45944

Linux kernel: iommu/vt-d: Clear Present bit before tearing down context entry

In the Linux kernel, the following vulnerability has been resolved: iommu/vt-d: Clear Present bit before tearing down context entry When tearing down a context entry, the current implementation zeros the entire 128-bit entry using multiple 64-bit writes.

At a glance

Exploited
Not known
Severity
7.5 High (CVSS 3.1)
Chance of exploitation
0.1% in the next 30 days
Sources
1 source

What to do

Check the vendor advisory for affected versions and fixes.

Read NVD CVE-2026-45944 (opens a new tab)

What happened

In the Linux kernel, the following vulnerability has been resolved:

iommu/vt-d: Clear Present bit before tearing down context entry

When tearing down a context entry, the current implementation zeros the entire 128-bit entry using multiple 64-bit writes. This creates a window where the hardware can fetch a "torn" entry — where some fields are already zeroed while the 'Present' bit is still set — leading to unpredictable behavior or spurious faults.

While x86 provides strong write ordering, the compiler may reorder writes to the two 64-bit halves of the context entry. Even without compiler reordering, the hardware fetch is not guaranteed to be atomic with respect to multiple CPU writes.

Continue reading

Align with the "Guidance to Software for Invalidations" in the VT-d spec (Section 6.5.3.3) by implementing the recommended ownership handshake:

1. Clear only the 'Present' (P) bit of the context entry first to signal the transition of ownership from hardware to software. 2. Use dma_wmb() to ensure the cleared bit is visible to the IOMMU. 3. Perform the required cache and context-cache invalidation to ensure hardware no longer has cached references to the entry. 4. Fully zero out the entry only after the invalidation is complete.

Also, add a dma_wmb() to context_set_present() to ensure the entry is fully initialized before the 'Present' bit becomes visible.

Scores and how they were measured

CVSS base severity

7.5

Version 3.1As of

CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.1%

Scored Percentile 2.1%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    NVD CVE-2026-45944 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  2. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  3. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  4. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  5. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-45944, scored 2026-10-30. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 30). Linux kernel: iommu/vt-d: Clear Present bit before tearing down context entry (CVE-2026-45944). https://kevwire.com/record/CVE-2026-45944

MLA

"Linux kernel: iommu/vt-d: Clear Present bit before tearing down context entry (CVE-2026-45944)." KEVWire, 30 Oct. 2026, kevwire.com/record/CVE-2026-45944.

Chicago

KEVWire. "Linux kernel: iommu/vt-d: Clear Present bit before tearing down context entry (CVE-2026-45944)." Last modified October 30, 2026. https://kevwire.com/record/CVE-2026-45944.

Evidence summary (plain text)

Linux kernel: iommu/vt-d: Clear Present bit before tearing down context entry (May 27, 2026).
In the Linux kernel, the following vulnerability has been resolved:

iommu/vt-d: Clear Present bit before tearing down context entry

When tearing down a context entry, the current implementation zeros the
entire 128-bit entry using multiple 64-bit writes. This creates a window
where the hardware can fetch a "torn" entry — where some fields are
already zeroed while the 'Present' bit is still set — leading to
unpredictable behavior or spurious faults.

While x86 provides strong write ordering, the compiler may reorder writes
to the two 64-bit halves of the context entry.
CVSS 7.5 (version 3.1; evidence as of Oct 30, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-45944).
EPSS 0.1% for the following 30 days, scored Oct 30, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-45944&date=2026-10-30).
Sources:
NVD CVE-2026-45944: https://nvd.nist.gov/vuln/detail/CVE-2026-45944
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T13:06:45.042Z&lastModEndDate=2026-10-30T14:50:57.069Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T12:22:16.957Z&lastModEndDate=2026-10-30T14:05:57.373Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T11:45:59.009Z&lastModEndDate=2026-10-30T13:20:57.281Z&resultsPerPage=500&startIndex=0
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-45944&date=2026-10-30
Record ID: CVE-2026-45944.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 30, 2026, 14:52 UTC. Ingestion is not an independent editorial investigation.

NVD status: Modified. Publication in the NVD is not evidence of exploitation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

Record JSON

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Record details

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