CVE-2026-43477

/// Technical description

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, a

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References