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CVE-2026-72397
hwmon: (pmbus/core) honor vrm_version in pmbus_data2reg_vid()
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem drivers/hwmon. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-72397 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | vulnerable | 6.12.113-1 | No fix published anywhere yet, neither in Debian nor upstream for the series trixie tracks. Watch the Debian tracker page for this CVE. Advisories for trixie have historically landed a median of 11 days after publication. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
pmbus_data2reg_vid() hardcoded the VR11 encoding regardless of the vrm_version configured by the driver, while pmbus_reg2data_vid() already switched on it. Any driver that selects a non-VR11 VID mode and exposes a regulator (or hwmon vout setter) sent dangerously wrong codes to PMBUS_VOUT_COMMAND -- e.g. an nvidia195mv part asked for 200 mV got the VR11 clamp to 500 mV encoded as 0xB2, which the chip interprets as 1080 mV. Mirror pmbus_reg2data_vid() so writes round-trip with reads.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
drivers/hwmon/pmbus/pmbus_core.c
- What this is
- HARDWARE MONITORINGMAINTAINERS section matched on drivers/hwmon/ · linux-hwmon@vger.kernel.org · Maintained
- Kernel module
- pmbus_core
Check it on the machine
grep -wE 'CONFIG_HWMON|CONFIG_PMBUS' /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w pmbus_corePrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookwormMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt/amd64, arm64/arm64, arm64/cloud-arm64, arm64/rt/arm64, i386/686, i386/686-pae, i386/rt/686-pae, ppc64el/powerpc64le
- trixie, forky, sidMnot built on amd64/cloud-amd64, arm64/cloud-arm64
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_HWMON, CONFIG_PMBUS
- Reads as
- all on means the file is compiled; any one off means it is not.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-08-15 (2 months ago)source
- CVSS
- 7.1 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.15%, higher than 3.9% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/hwmon
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.3 | 7.1.5 | 5bd0d4764039 |
| 4.3 | 7.2 | 828cd614e2af |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The bug is only reached from local host interfaces—writable hwmon sysfs attributes (pmbus_set_sensor) and the PMBus regulator set_voltage path (pmbus_regulator_set_voltage)—which encode values and issue I2C PMBUS_VOUT_COMMAND writes; there is no network, adjacent-radio, or direct physical-access entry point.
- AC:LAttack complexity, low
- On systems with non-VR11 VID PMBus controllers (VR12/VR13/IMVP9/AMD/nvidia195mv), any voltage-setting write deterministically uses the wrong VR11 encoding with no race, timing window, or uncontrollable memory layout; the attacker fully controls the written millivolt value and can repeat the operation reliably.
- PR:LPrivileges required, low
- Writable hwmon limit attributes are exposed as mode 0644 with no capability check in pmbus_set_sensor, so a local uid-0 context (including user-namespace root or container root with /sys access) can drive the bad encoding; regulator consumers can also be influenced from ordinary local workloads on affected server/GPU platforms.
- UI:NUser interaction, none
- Exploitation requires only the attacker (or attacker-controlled software) to write hwmon voltage limits or invoke regulator voltage changes; no separate victim interaction such as plugging hardware or approving a prompt is needed.
- S:UScope, unchanged
- Impact is confined to misprogramming PMBus voltage rails on the same host kernel authority; it does not cross VM, IOMMU, or sandbox boundaries and is not a guest-to-host escape.
- C:NConfidentiality impact, none
- This is a write-side VID encoding logic error, not kernel memory corruption; reads use the correct pmbus_reg2data_vid path and the flaw does not disclose kernel pointers, arbitrary memory, or other confidential data.
- I:HIntegrity impact, high
- Incorrect VID-to-register conversion sends dangerously wrong PMBUS_VOUT_COMMAND values to hardware (e.g., 200 mV requested on nvidia195mv becomes 1080 mV applied), corrupting critical CPU/GPU/board power-rail configuration and potentially causing permanent hardware damage.
- A:HAvailability impact, high
- Severe over- or under-voltage on core power rails can trigger immediate hardware protection shutdowns, system hangs/resets, and sustained denial of service on data-center, HPC, and GPU server deployments using affected PMBus VRM controllers.