# CVE-2026-64476: vfio/pci: Latch disable_idle_d3 per device

> A race condition in Linux kernel vfio-pci allows unbalanced power management operations, potentially causing denial of service.

- **Severity:** Not scored
- **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:** 25 Jul 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-64476, DEBIAN-CVE-2026-64476, GHSA-mcmr-g6rj-vcxr, ROOT-OS-UBUNTU-2204-CVE-2026-64476, UBUNTU-CVE-2026-64476

## What is CVE-2026-64476?

CVE-2026-64476 is a vulnerability in Linux, published on 25 Jul 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:

vfio/pci: Latch disable_idle_d3 per device

When disable_idle_d3 was introduced in vfio-pci, it directly manipulated
the device power state with pci_set_power_state().  There were no
refcounts to maintain or balanced operations, we could unconditionally
bring the device to D0 and conditionally move it to D3hot.  Therefore
the module parameter was made writable.

Later, in commit c61302aa48f7 ("vfio/pci: Move module parameters to
vfio_pci.c"), as part of the vfio-pci-core split, the writable aspect
of the module parameter was nullified.  The parameter value could still
be changed through sysfs, but the vfio-pci driver latched the values
into vfio-pci-core globals at module init.  Loading the vfio-pci module,
or unloading and reloading, with non-default or different values could
change the globals relative to existing devices bound to vfio-pci
variant drivers.

Runtime PM was introduced in commit 7ab5e10eda02 ("vfio/pci: Move the
unused device into low power state with runtime PM"), which marks the
point where power states became refcounted.  PM get and put operations
need to be balanced, but the same module operations noted above can
change the global variables relative to those devices already bound to
vfio-pci variant drivers.  This introduces a window where PM operations
can now become unbalanced.

To resolve this with a narrow footprint for stable backports, the
disable_idle_d3 flag is latched into the vfio_pci_core_device at the
time of initialization, such that the device always operates with a
consistent value.

NB. vfio_pci_dev_set_try_reset() now unconditionally raises the
runtime PM usage count around bus reset to account for disable_idle_d3
becoming a per-device rather than global flag.  When this flag is set,
the additional get/put pair is harmless and allows continued use of the
shared vfio_pci_dev_set_pm_runtime_get() helper.

## Which versions are affected by CVE-2026-64476?


## How do I fix CVE-2026-64476?

Apply the vendor's patch.

## Is CVE-2026-64476 being exploited?

There is no known exploitation of CVE-2026-64476 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64476 and fix it if it is affected.

What it is: CVE-2026-64476 is a vulnerability in Linux, published on 25 Jul 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-2026-64476 in the wild and no public exploit code.

Affected product: Linux. 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-2026-64476/ (Markdown: https://insights.sbomify.com/CVE-2026-64476/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64476
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64476
- OSV: https://osv.dev/vulnerability/CVE-2026-64476

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64476/
Summaries are generated and may contain mistakes; the official description above is the record.