CVE-2021-47067

What it actually does

Causes a lockup in the Tegra voltage coupler when voltage-spread exceeds the max-spread requirement for a CPU regulator that has no consumers.

Why it matters to the business

Produces system hangs on affected embedded devices when dynamic voltage scaling is enabled, interrupting operations and requiring reboots.

How an attack unfolds

An attacker or misconfigured workload enables system-wide DVFS via device tree on Tegra30 hardware, driving the voltage-spread value outside the supported range and triggering the regulator deadlock.

How to fix it

Apply the upstream fix in soc/tegra regulators that accounts for max-spread when the CPU regulator has no consumers; update to a kernel containing commit resolving CVE-2021-47067.

How to confirm the fix worked

Inspect kernel logs for regulator lockup messages, confirm presence of the max-spread accounting logic in the tegra regulator driver, and test DVFS enablement on representative hardware.

Typical attack path

1. Modify device tree to enable system-wide DVFS
2. Boot on vulnerable Tegra30 hardware
3. Allow regulator code path to evaluate a consumer-less CPU regulator with out-of-range spread
4. Induce lockup in the voltage coupler

How to detect it

Search kernel logs for regulator or voltage coupler lockup entries around DVFS enablement events; correlate with Tegra30 boot sequences.

What your security team should do

• Prioritize kernel updates on all Tegra-based systems
• Review device trees for DVFS settings before enabling system-wide scaling
• Monitor EPSS and exploit maturity; maintain standard patch cadence given low exploitation likelihood