# CVE-2026-90311: thermal: hwmon: Remove hwmon class device along with its parent

> A use-after-free vulnerability in the Linux kernel thermal subsystem allows local attackers to cause a denial of service by triggering improper device removal.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-102362, BELL-CVE-2026-90311, DEBIAN-CVE-2026-90311, GHSA-43gv-wm7g-h6q4, UBUNTU-CVE-2026-90311

## What is CVE-2026-90311?

CVE-2026-90311 is an use after free vulnerability in Linux, published on 17 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

thermal: hwmon: Remove hwmon class device along with its parent

The current code creates one hwmon device per thermal zone type and that
device is registered under the first thermal zone of the given type.

That turns out to be problematic when the thermal zone holding the
hwmon device is removed.

For example, say that there are two ACPI thermal zones on a system

 /sys/devices/virtual/thermal/thermal_zone0/
 /sys/devices/virtual/thermal/thermal_zone1/

The current code registers a hwmon class device for thermal_zone0 only:

 /sys/devices/virtual/thermal/thermal_zone0/hwmon0/

because the type is "acpitz" for both of them, but it adds a sysfs
attribute that belongs to thermal_zone1 under it:

 /sys/devices/virtual/thermal/thermal_zone0/hwmon0/temp2_input

There is also

 /sys/devices/virtual/thermal/thermal_zone0/hwmon0/temp1_input

which belongs to thermal_zone0.

When thermal_zone0 is removed, say because the ACPI thermal driver is
unbound from the underlying platform device, thermal_remove_hwmon_sysfs()
skips the removal of hwmon0 because of the temp2_input attribute
belonging to thermal_zone1 which effectively prevents thermal_zone0
removal from making progress.

Address this by making thermal_remove_hwmon_sysfs() remove the entire
hwmon class device interface for the given thermal zone type when the
thermal zone device holding it is removed.

To prevent races with thermal_add_hwmon_sysfs() that may interfere
with this, carry out the entire addition and removal of hwmon sysfs
interfaces for thermal zones under thermal_hwmon_list_lock.

Also adjust the layout of the labels in thermal_add_hwmon_sysfs() to
the current kernel coding style to align with the new "unlock" label.

## Which versions are affected by CVE-2026-90311?


## How do I fix CVE-2026-90311?

Apply the vendor's patch.

## Is CVE-2026-90311 being exploited?

There is no known exploitation of CVE-2026-90311 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90311 and fix it if it is affected.

What it is: CVE-2026-90311 is an use after free vulnerability in Linux, published on 17 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-90311 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-90311/ (Markdown: https://insights.sbomify.com/CVE-2026-90311/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90311
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90311
- OSV: https://osv.dev/vulnerability/CVE-2026-90311

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90311/
Summaries are generated and may contain mistakes; the official description above is the record.