# CVE-2026-43161: iommu/vt-d: Skip dev-iotlb flush for inaccessible PCIe device without scalable mode

> A Linux kernel IOMMU bug causes a host hard-lock when a PCIe device link drops without scalable mode, requiring a patch to prevent denial of service.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 May 2026
- **Updated:** 23 May 2026
- **Also known as:** AZL-85800, BELL-CVE-2026-43161, DEBIAN-CVE-2026-43161, GHSA-jph2-qvw9-vvwq, ROOT-OS-DEBIAN-12-CVE-2026-43161, ROOT-OS-UBUNTU-2204-CVE-2026-43161, ROOT-OS-UBUNTU-2404-CVE-2026-43161, UBUNTU-CVE-2026-43161

## What is CVE-2026-43161?

CVE-2026-43161 is a medium-severity denial of service vulnerability in Linux kernel, published on 6 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: Skip dev-iotlb flush for inaccessible PCIe device without scalable mode

PCIe endpoints with ATS enabled and passed through to userspace
(e.g., QEMU, DPDK) can hard-lock the host when their link drops,
either by surprise removal or by a link fault.

Commit 4fc82cd907ac ("iommu/vt-d: Don't issue ATS Invalidation
request when device is disconnected") adds pci_dev_is_disconnected()
to devtlb_invalidation_with_pasid() so ATS invalidation is skipped
only when the device is being safely removed, but it applies only
when Intel IOMMU scalable mode is enabled.

With scalable mode disabled or unsupported, a system hard-lock
occurs when a PCIe endpoint's link drops because the Intel IOMMU
waits indefinitely for an ATS invalidation that cannot complete.

Call Trace:
 qi_submit_sync
 qi_flush_dev_iotlb
 __context_flush_dev_iotlb.part.0
 domain_context_clear_one_cb
 pci_for_each_dma_alias
 device_block_translation
 blocking_domain_attach_dev
 iommu_deinit_device
 __iommu_group_remove_device
 iommu_release_device
 iommu_bus_notifier
 blocking_notifier_call_chain
 bus_notify
 device_del
 pci_remove_bus_device
 pci_stop_and_remove_bus_device
 pciehp_unconfigure_device
 pciehp_disable_slot
 pciehp_handle_presence_or_link_change
 pciehp_ist

Commit 81e921fd3216 ("iommu/vt-d: Fix NULL domain on device release")
adds intel_pasid_teardown_sm_context() to intel_iommu_release_device(),
which calls qi_flush_dev_iotlb() and can also hard-lock the system
when a PCIe endpoint's link drops.

Call Trace:
 qi_submit_sync
 qi_flush_dev_iotlb
 __context_flush_dev_iotlb.part.0
 intel_context_flush_no_pasid
 device_pasid_table_teardown
 pci_pasid_table_teardown
 pci_for_each_dma_alias
 intel_pasid_teardown_sm_context
 intel_iommu_release_device
 iommu_deinit_device
 __iommu_group_remove_device
 iommu_release_device
 iommu_bus_notifier
 blocking_notifier_call_chain
 bus_notify
 device_del
 pci_remove_bus_device
 pci_stop_and_remove_bus_device
 pciehp_unconfigure_device
 pciehp_disable_slot
 pciehp_handle_presence_or_link_change
 pciehp_ist

Sometimes the endpoint loses connection without a link-down event
(e.g., due to a link fault); killing the process (virsh destroy)
then hard-locks the host.

Call Trace:
 qi_submit_sync
 qi_flush_dev_iotlb
 __context_flush_dev_iotlb.part.0
 domain_context_clear_one_cb
 pci_for_each_dma_alias
 device_block_translation
 blocking_domain_attach_dev
 __iommu_attach_device
 __iommu_device_set_domain
 __iommu_group_set_domain_internal
 iommu_detach_group
 vfio_iommu_type1_detach_group
 vfio_group_detach_container
 vfio_group_fops_release
 __fput

pci_dev_is_disconnected() only covers safe-removal paths;
pci_device_is_present() tests accessibility by reading
vendor/device IDs and internally calls pci_dev_is_disconnected().
On a ConnectX-5 (8 GT/s, x2) this costs ~70 µs.

Since __context_flush_dev_iotlb() is only called on
{attach,release}_dev paths (not hot), add pci_device_is_present()
there to skip inaccessible devices and avoid the hard-lock.

## Which versions are affected by CVE-2026-43161?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43161?

Apply the vendor's patch.

## Is CVE-2026-43161 being exploited?

There is no known exploitation of CVE-2026-43161 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-2026-43161 and fix it if it is affected.

What it is: CVE-2026-43161 is a medium-severity denial of service vulnerability in Linux kernel, published on 6 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-2026-43161 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-2026-43161/ (Markdown: https://insights.sbomify.com/CVE-2026-43161/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43161
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43161
- OSV: https://osv.dev/vulnerability/CVE-2026-43161

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43161/
Summaries are generated and may contain mistakes; the official description above is the record.