# CVE-2026-45944: iommu/vt-d: Clear Present bit before tearing down context entry

> A race condition in the Linux kernel IOMMU driver can cause spurious faults or unpredictable behavior during context entry teardown.

- **Severity:** High 7.5 (`CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 May 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-88749, BELL-CVE-2026-45944, DEBIAN-CVE-2026-45944, GHSA-xp3w-6f4f-gvg7, ROOT-OS-DEBIAN-11-CVE-2026-45944, ROOT-OS-DEBIAN-12-CVE-2026-45944, ROOT-OS-DEBIAN-13-CVE-2026-45944, ROOT-OS-UBUNTU-2204-CVE-2026-45944, ROOT-OS-UBUNTU-2404-CVE-2026-45944, UBUNTU-CVE-2026-45944

## What is CVE-2026-45944?

CVE-2026-45944 is a high-severity vulnerability in Linux kernel, published on 27 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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.

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.

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2026-45944?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-45944?

Apply the vendor's patch.

## Is CVE-2026-45944 being exploited?

There is no known exploitation of CVE-2026-45944 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-45944 and fix it if it is affected.

What it is: CVE-2026-45944 is a high-severity vulnerability in Linux kernel, published on 27 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-45944 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-45944/ (Markdown: https://insights.sbomify.com/CVE-2026-45944/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45944
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45944
- OSV: https://osv.dev/vulnerability/CVE-2026-45944

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45944/
Summaries are generated and may contain mistakes; the official description above is the record.