# CVE-2026-89803: drm/nouveau: unsubscribe the channel-kill event before the fence context

> A use-after-free in the nouveau driver allows attackers to cause a denial of service or potentially execute code via a race condition during channel destruction.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** 16 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-101430, BELL-CVE-2026-89803, DEBIAN-CVE-2026-89803, GHSA-6w43-3678-pp8f, UBUNTU-CVE-2026-89803

## What is CVE-2026-89803?

CVE-2026-89803 is a high-severity use after free vulnerability in Linux, published on 16 Sep 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/nouveau: unsubscribe the channel-kill event before the fence context

nouveau_channel_del() tears the fence context down first and only drops
the channel-kill subscription later, in the middle of the nvif object
teardown:

	if (chan->fence)
		nouveau_fence(chan->cli->drm)->context_del(chan);
	...
	nvif_object_dtor(&chan->vram);
	nvif_event_dtor(&chan->kill);

The subscribed handler is nouveau_channel_killed(), which calls
nouveau_channel_kill() and from there nouveau_fence_context_kill() on
chan->fence. A kill event delivered in that window takes fctx->lock and
walks fctx->pending on a fence context that context_del() has already
freed.

Nothing reaches this below Fermi today, because the subscription is
gated on FERMI_CHANNEL_GPFIFO and nothing kills a channel there. On
Fermi and newer the window is real but narrow, since a kill has to land
exactly while the channel is being destroyed. That is reason enough on
its own, which is why this carries a Fixes: tag. The last patch in this
series subscribes Tesla channels as well; nothing kills those today, so
it does not widen the exposure now, but it is the groundwork for a
recovery path that would, and the ordering is better fixed before that
lands than alongside it.

Drop the subscription before anything it depends on is torn down.

## Which versions are affected by CVE-2026-89803?


## How do I fix CVE-2026-89803?

Apply the vendor's patch.

## Is CVE-2026-89803 being exploited?

There is no known exploitation of CVE-2026-89803 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89803 and fix it if it is affected.

What it is: CVE-2026-89803 is a high-severity use after free vulnerability in Linux, published on 16 Sep 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-2026-89803 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-2026-89803/ (Markdown: https://insights.sbomify.com/CVE-2026-89803/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89803
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89803
- OSV: https://osv.dev/vulnerability/CVE-2026-89803

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89803/
Summaries are generated and may contain mistakes; the official description above is the record.