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.
- 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
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.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-89803 being exploited?
There is no known exploitation of CVE-2026-89803 in the wild and no public exploit code.
Sources
Also known as AZL-101430, BELL-CVE-2026-89803, DEBIAN-CVE-2026-89803, GHSA-6w43-3678-pp8f, UBUNTU-CVE-2026-89803.