# CVE-2026-98309: drm/vc4: Use managed KMS polling to fix UAF on unbind

> A use-after-free vulnerability in the Linux kernel vc4 driver allows local attackers with root privileges to cause a system crash or potentially execute code during device unbinding.

- **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:** 6 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-106062, BELL-CVE-2026-98309, DEBIAN-CVE-2026-98309, GHSA-fcmj-9h4r-58r4, UBUNTU-CVE-2026-98309

## What is CVE-2026-98309?

CVE-2026-98309 is an use after free vulnerability in Linux, published on 6 Oct 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:

drm/vc4: Use managed KMS polling to fix UAF on unbind

vc4_kms_load() calls drm_kms_helper_poll_init() but the driver provides
no matching drm_kms_helper_poll_fini(). The output poll work stays
scheduled after unbind and runs on the freed drm_device:

  # modprobe vc4; rmmod vc4; sleep 10
  BUG: KASAN: slab-use-after-free in delayed_work_timer_fn
  BUG: KASAN: slab-use-after-free in drm_client_dev_hotplug [drm]
  Workqueue: events output_poll_execute [drm_kms_helper]
  Allocated by task 171: __devm_drm_dev_alloc
  Freed by task 262 (rmmod): drm_dev_put / component_del

Use drmm_kms_helper_poll_init() so polling is finalized with the device,
as other drivers do.

## Which versions are affected by CVE-2026-98309?


## How do I fix CVE-2026-98309?

Apply the vendor's patch.

## Is CVE-2026-98309 being exploited?

There is no known exploitation of CVE-2026-98309 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98309 and fix it if it is affected.

What it is: CVE-2026-98309 is an use after free vulnerability in Linux, published on 6 Oct 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-2026-98309 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-2026-98309/ (Markdown: https://insights.sbomify.com/CVE-2026-98309/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98309
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98309
- OSV: https://osv.dev/vulnerability/CVE-2026-98309

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98309/
Summaries are generated and may contain mistakes; the official description above is the record.