# CVE-2026-64472: vfio/mlx5: Fix racy bitfields and tighten struct layout

> A race condition in the Linux kernel vfio/mlx5 driver allows local attackers to cause denial of service or potentially escalate privileges via concurrent bitfield updates.

- **Severity:** Not scored
- **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:** 25 Jul 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-64472, DEBIAN-CVE-2026-64472, GHSA-3wrg-mvh6-9v25, ROOT-OS-UBUNTU-2204-CVE-2026-64472, UBUNTU-CVE-2026-64472

## What is CVE-2026-64472?

CVE-2026-64472 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/mlx5: Fix racy bitfields and tighten struct layout

Bitfield operations are not atomic, they use a read-modify-write
pattern, therefore we should be careful not to pack bitfields that
can be concurrently updated into the same storage unit.

This split takes a binary approach: flags that are only modified
pre/post open/close remain bitfields, flags modified from user
action, including actions that reach across to another device (ex.
reset) use dedicated storage units.

Note mlx5_vhca_page_tracker.status is relocated to fill the alignment
hole this split exposes.

Bitfield justifications:

  migrate_cap: written only in mlx5vf_cmd_set_migratable() at probe
  chunk_mode: written only in mlx5vf_cmd_set_migratable() at probe
  mig_state_cap: written only in mlx5vf_cmd_set_migratable() at probe

Dedicated storage units:

  mdev_detach: written in the VF attach/detach event notifier
               mlx5fv_vf_event() at runtime
  log_active: written in mlx5vf_start_page_tracker()/
              mlx5vf_stop_page_tracker() during runtime dirty tracking
  deferred_reset: written in mlx5vf_state_mutex_unlock()/
                  mlx5vf_pci_aer_reset_done() during runtime reset handling
  is_err: set by tracker error handling and dirty-log polling at runtime
  object_changed: set by tracker event handling and cleared by dirty-log
                  polling at runtime

## Which versions are affected by CVE-2026-64472?


## How do I fix CVE-2026-64472?

Apply the vendor's patch.

## Is CVE-2026-64472 being exploited?

There is no known exploitation of CVE-2026-64472 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64472 and fix it if it is affected.

What it is: CVE-2026-64472 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-2026-64472 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-2026-64472/ (Markdown: https://insights.sbomify.com/CVE-2026-64472/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64472
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64472
- OSV: https://osv.dev/vulnerability/CVE-2026-64472

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64472/
Summaries are generated and may contain mistakes; the official description above is the record.