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CVE-2026-89803
drm/nouveau: unsubscribe the channel-kill event before the fence context
Published 2026-09-16 (33 days ago) by the Linux kernel CNA. Subsystem drivers/gpu. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-89803 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
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.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
drivers/gpu/drm/nouveau/nouveau_chan.c
- What this is
- DRM DRIVER FOR NVIDIA GEFORCE/QUADRO GPUSMAINTAINERS section matched on drivers/gpu/drm/nouveau/ · dri-devel@lists.freedesktop.org · Supported
- Kernel module
- nouveau
Check it on the machine
grep -w CONFIG_DRM_NOUVEAU /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w nouveauPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookwormMnot built on amd64/cloud-amd64, arm64/cloud-arm64
- trixieMnot built on amd64/cloud-amd64, arm64/cloud-arm64, armel/rpi, s390x/s390x
- forky, sidMnot built on amd64/cloud-amd64, arm64/cloud-arm64, s390x/s390x
- bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/cloud-arm64
- M
- a module where it is built at all; some flavours do not build it
- Build switch
- CONFIG_DRM_NOUVEAU
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-09-16 (33 days ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.16%, higher than 5.2% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/gpu
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.6 | 6.12.110 | f5a79a9ebfba |
| 5.6 | 6.18.51 | f3830fdd6930 |
| 5.6 | 7.2.5 | 1fef7553dc62 |
| 5.6 | 7.3 | 511585987d27 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- Reached via local DRM ioctls DRM_IOCTL_NOUVEAU_CHANNEL_ALLOC/FREE on /dev/dri/renderD*, or by closing that fd (nouveau_drm_postclose→nouveau_abi16_chan_fini→nouveau_channel_del). Not reachable from network protocols, adjacent radios, or physical buses.
- AC:LAttack complexity, low
- The attacker creates and destroys their own Fermi+ channel so the kill handler stays armed across fence teardown; they also induce the kill (illegal pushbuf/MMU fault or GSP RC during the still-subscribed nvif object dtors) and can retry, so they control both sides of the race.
- PR:LPrivileges required, low
- CHANNEL_ALLOC and CHANNEL_FREE are DRM_RENDER_ALLOW with no ROOT_ONLY or capability checks. Any unprivileged local user who can open the nouveau render node (render/video group, logind ACL, Android GPU, or container) can trigger it.
- UI:NUser interaction, none
- The attacker opens their own nouveau render-node client and issues CHANNEL_ALLOC/FREE or close on that fd; no separate victim action is required.
- S:UScope, unchanged
- The use-after-free corrupts host kernel heap state (struct nouveau_fence_chan) inside the nouveau driver. Impact stays in the same kernel authority; this is not a VM escape or IOMMU/DMA isolation bypass.
- C:HConfidentiality impact, high
- A channel-kill delivered after context_del uses chan->fence on a freed fence context, taking fctx->lock and walking fctx->pending. Reclaiming that slab enables arbitrary kernel reads as with other UAFs.
- I:HIntegrity impact, high
- The same UAF lets the IRQ/GSP kill path list_del and dma_fence_signal through attacker-reclaimed fence-context and pending-list pointers, enabling heap corruption, arbitrary writes, and control-flow hijack.
- A:HAvailability impact, high
- Dereferencing the freed fence context from nouveau_channel_killed() (spinlock/list walk in interrupt or GSP callback) oopses or panics the kernel; the attacker can repeat CHANNEL_FREE or close to crash the system.