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CVE-2026-63850
drm/amdgpu/vcn: set no_user_fence for VCN v5.0.0 enc ring
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem drivers/gpu. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-63850 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
VCN encoder and decoder rings do not support 64-bit user fence writes, reject CS submissions with user fences. (cherry picked from commit 49b1fbbb5a071197ee71e2d70959b1cb29bdc317)
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/amd/amdgpu/vcn_v5_0_0.c
- What this is
- RADEON and AMDGPU DRM DRIVERSMAINTAINERS section matched on drivers/gpu/drm/amd/ · amd-gfx@lists.freedesktop.org · Supported
- Kernel module
- amdgpu
Check it on the machine
grep -w CONFIG_DRM_AMDGPU /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 amdgpuPrints 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. The build rule could not be established for 1 release, so nothing is claimed about those.
- bookworm?
- trixieMnot built on amd64/cloud-amd64, arm64/cloud-arm64, armel/rpi, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, s390x/s390x
- forky, sidMnot built on amd64/cloud-amd64, arm64/cloud-arm64, s390x/s390x
- ?
- not established - no Makefile entry for the affected file
- M
- a module where it is built at all; some flavours do not build it
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
- Build switch
- CONFIG_DRM_AMDGPU
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
- 2026-07-19 (3 months 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
- 0.18%, higher than 6.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- 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 |
|---|---|---|
| 6.9 | 6.12.91 | 9f5a1459ecc3 |
| 6.9 | 6.18.33 | 139a8a52ef43 |
| 6.9 | 7.0.10 | 2c350f3cd94b |
| 6.9 | 7.1 | 8cae0ce77de4 |
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
- The vulnerable code is reached via the local DRM_IOCTL_AMDGPU_CS ioctl on an AMDGPU render node (/dev/dri/renderD*), submitting a command buffer with AMDGPU_CHUNK_ID_FENCE to the VCN v5.0.0 encoder ring.
- AC:LAttack complexity, low
- An attacker with render-node access can deterministically submit a VCN encoder CS with a user-fence chunk; no race, special memory layout, or non-default kernel configuration is required beyond having affected AMD VCN 5.0.0 hardware.
- PR:LPrivileges required, low
- Exploitation requires access to the AMDGPU DRM render node, which is available to unprivileged local users in the render/video group (or equivalent GPU access), not root or capabilities obtainable only in the init namespace.
- UI:NUser interaction, none
- No victim interaction is needed beyond the attacker already having GPU render-node access; exploitation is fully attacker-driven through ioctl submission.
- S:UScope, unchanged
- Impact is kernel/GPU memory corruption and privilege escalation within the same host security boundary; it does not inherently cross a VM, container, or IOMMU isolation boundary.
- C:HConfidentiality impact, high
- Submitting an unsupported 64-bit user fence causes the VCN hardware to perform misdirected GPU memory writes, providing a memory-corruption primitive that can be leveraged for arbitrary kernel memory disclosure.
- I:HIntegrity impact, high
- The malformed fence write gives the attacker a GPU-initiated arbitrary write primitive within the GPU virtual address space, enabling memory corruption and potential kernel code execution.
- A:HAvailability impact, high
- Malformed VCN fence commands can hang the GPU, trigger kernel oopses, or crash the system when the unsupported fence operation is processed by hardware.