# CVE-2026-43477: drm/i915/vrr: Configure VRR timings after enabling TRANS_DDI_FUNC_CTL

Status: published. Published: 2026-05-13. Updated: 2026-11-06.

In the Linux kernel, the following vulnerability has been resolved:

drm/i915/vrr: Configure VRR timings after enabling TRANS_DDI_FUNC_CTL

Apparently ICL may hang with an MCE if we write TRANS_VRR_VMAX/FLIPLINE
before enabling TRANS_DDI_FUNC_CTL.

Personally I was only able to reproduce a hang (on an Dell XPS 7390
2-in-1) with an external display connected via a dock using a dodgy
type-C cable that made the link training fail. After the failed
link training the machine would hang. TGL seemed immune to the
problem for whatever reason.

BSpec does tell us to configure VRR after enabling TRANS_DDI_FUNC_CTL
as well. The DMC firmware also does the VRR restore in two stages:
- first stage seems to be unconditional and includes TRANS_VRR_CTL
  and a few other VRR registers, among other things
- second stage is conditional on the DDI being enabled,
  and includes TRANS_DDI_FUNC_CTL and TRANS_VRR_VMAX/VMIN/FLIPLINE,
  among other things

So let's reorder the steps to match to avoid the hang, and
toss in an extra WARN to make sure we don't screw this up later.

BSpec: 22243
(cherry picked from commit 93f3a267c3dd4d811b224bb9e179a10d81456a74)

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ dda7dcd9da73c5327aef42b89f0519bb51e84217; < 8a7d29b8bda144d44e61df1b2705b1d4378f4e44 (affected, git); ≥ dda7dcd9da73c5327aef42b89f0519bb51e84217; < bf9e3b6ffd76da38dd4961c65d80571b25bf10a5 (affected, git); ≥ dda7dcd9da73c5327aef42b89f0519bb51e84217; < 237aab549676288d9255bb8dcc284738e56eaa31 (affected, git). Source: CNA: Linux
- Linux / Linux: 6.16 (affected); ≥ 0; < 6.16 (unaffected, semver); ≥ 6.18.20; ≤ 6.18.* (unaffected, semver); ≥ 6.19.9; ≤ 6.19.* (unaffected, semver); ≥ 7.0; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: 0.11% as of 2026-11-06; percentile 1.40%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: Not reported

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/8a7d29b8bda144d44e61df1b2705b1d4378f4e44 (CNA: Linux)

- https://git.kernel.org/stable/c/bf9e3b6ffd76da38dd4961c65d80571b25bf10a5 (CNA: Linux)

- https://git.kernel.org/stable/c/237aab549676288d9255bb8dcc284738e56eaa31 (CNA: Linux)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-43477; retrieved 2026-11-06; source updated 2026-11-06

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-43477; retrieved 2026-11-06; source updated Not reported

Revision: 8f373c75cd215265a5ecc6cf64de0cf86b10cb51e22345066d0f7f4fe301231b

Canonical: https://y2.dev/cve/CVE-2026-43477

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