CVE-2026-45894High· 7.8▾ Twilight

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

In the Linux kernel, the following vulnerability has been resolved: iommu/vt-d: Clear Present bit before tearing down PASID entry The Intel VT-d Scalable Mode PASID table entry consists of 512 bits (64 bytes). When tearing down an entr…

▾ Twilight zone — High severity, or a signal on a lesser flaw

Depth score43/ 100 · Moderate

impact 42.9 · likelihood 0 · exploitation 0

⚡ Agent-ready:Raw markdown ↗JSON ↗

Proof of concept

Need a working PoC? Pro members can cast a request and our team develops one — it lands right here.

…

Published

May 27, 2026

Updated

Oct 21, 2026

CVSS

7.8

Vendor

Linux

Product

Linux

CWE

—

Depth score

43 · Moderate

EPSS

0.13% · p3

Platforms

—

Source

CVEORG

Vector

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

CISA SSVC

decided 2026-10-16

Exploitation: none
Automatable: no
Technical impact: total

Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake. The CVSS score shown above comes from the assigning CNA record, not NVD.

EPSS history

Exploit-prediction probability, daily snapshots since Oct 16.

0.1% → 0.1%

Timeline

Disclosure to exploitation, from the record and what we observed since indexing it.

3 events · 147 days

May 27, 2026Published
Disclosed via CVEORG
Oct 16, 2026EPSS first tracked
0.1%
Oct 21, 2026Record revised
Last analysed / modified upstream

Linux #cve.org

Affected

Linux >= 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 < c36b0515c6445bd137ec8ad86ef5470c45d6e4bf
Linux >= 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 < a84d30e8d2bacd21782a6481158b7c9c552f4868
Linux >= 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 < 821807c167b7b48a41b95b6607c6b9f97600f7d9
Linux >= 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 < 949d71666e9dd19f21e7b4b53a88cd2c5b902858
Linux >= 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 < 75ed00055c059dedc47b5daaaa2f8a7a019138ff
Linux 5.0

Full technical detail▾

Overview

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

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

The Intel VT-d Scalable Mode PASID table entry consists of 512 bits (64 bytes). When tearing down an entry, the current implementation zeros the entire 64-byte structure immediately using multiple 64-bit writes.

Since the IOMMU hardware may fetch these 64 bytes using multiple internal transactions (e.g., four 128-bit bursts), updating or zeroing the entire entry while it is active (P=1) risks a "torn" read. If a hardware fetch occurs simultaneously with the CPU zeroing the entry, the hardware could observe an inconsistent state, leading to unpredictable behavior or spurious faults.

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

Clear only the 'Present' (P) bit of the PASID entry.
Use a dma_wmb() to ensure the cleared bit is visible to hardware before proceeding.
Execute the required invalidation sequence (PASID cache, IOTLB, and Device-TLB flush) to ensure the hardware has released all cached references.
Only after the flushes are complete, zero out the remaining fields of the PASID entry.

Also, add a dma_wmb() in pasid_set_present() to ensure that all other fields of the PASID entry are visible to the hardware before the Present bit is set.

Affected

Linux >= 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 < c36b0515c6445bd137ec8ad86ef5470c45d6e4bf
Linux >= 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 < a84d30e8d2bacd21782a6481158b7c9c552f4868
Linux >= 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 < 821807c167b7b48a41b95b6607c6b9f97600f7d9
Linux >= 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 < 949d71666e9dd19f21e7b4b53a88cd2c5b902858
Linux >= 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 < 75ed00055c059dedc47b5daaaa2f8a7a019138ff
Linux 5.0

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

References

Related vulnerabilities

Connected by shared product, vendor, weakness, or advisory.

#cve.org

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

▾ Twilight zone — High severity, or a signal on a lesser flaw

Depth score43/ 100 · Moderate

impact 42.9 · likelihood 0 · exploitation 0

Overview

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

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

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

Clear only the 'Present' (P) bit of the PASID entry.

Use a dma_wmb() to ensure the cleared bit is visible to hardware before proceeding.

Execute the required invalidation sequence (PASID cache, IOTLB, and Device-TLB flush) to ensure the hardware has released all cached references.

Only after the flushes are complete, zero out the remaining fields of the PASID entry.

Also, add a dma_wmb() in pasid_set_present() to ensure that all other fields of the PASID entry are visible to the hardware before the Present bit is set.

Affected

Linux >= 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 < c36b0515c6445bd137ec8ad86ef5470c45d6e4bf

Linux >= 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 < a84d30e8d2bacd21782a6481158b7c9c552f4868

Linux >= 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 < 821807c167b7b48a41b95b6607c6b9f97600f7d9

Linux >= 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 < 949d71666e9dd19f21e7b4b53a88cd2c5b902858

Linux >= 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 < 75ed00055c059dedc47b5daaaa2f8a7a019138ff

Linux 5.0