# CVE-2025-71111: hwmon: (w83791d) Convert macros to functions to avoid TOCTOU

> A race condition in the w83791d hardware monitoring driver can cause divide-by-zero errors, leading to a denial of service.

- **Severity:** Medium 4.7 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 14 Jan 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2025-71111, DEBIAN-CVE-2025-71111, GHSA-w25h-64gv-grq6, ROOT-OS-UBUNTU-2204-CVE-2025-71111, ROOT-OS-UBUNTU-2404-CVE-2025-71111, UBUNTU-CVE-2025-71111

## What is CVE-2025-71111?

CVE-2025-71111 is a medium-severity vulnerability in Linux kernel, published on 14 Jan 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:

hwmon: (w83791d) Convert macros to functions to avoid TOCTOU

The macro FAN_FROM_REG evaluates its arguments multiple times. When used
in lockless contexts involving shared driver data, this leads to
Time-of-Check to Time-of-Use (TOCTOU) race conditions, potentially
causing divide-by-zero errors.

Convert the macro to a static function. This guarantees that arguments
are evaluated only once (pass-by-value), preventing the race
conditions.

Additionally, in store_fan_div, move the calculation of the minimum
limit inside the update lock. This ensures that the read-modify-write
sequence operates on consistent data.

Adhere to the principle of minimal changes by only converting macros
that evaluate arguments multiple times and are used in lockless
contexts.

Weakness: CWE-367 (Time-of-check Time-of-use (TOCTOU) Race Condition), CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2025-71111?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-71111?

Apply the vendor's patch.

## Is CVE-2025-71111 being exploited?

There is no known exploitation of CVE-2025-71111 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-71111 and fix it if it is affected.

What it is: CVE-2025-71111 is a medium-severity vulnerability in Linux kernel, published on 14 Jan 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-2025-71111 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2025-71111/ (Markdown: https://insights.sbomify.com/CVE-2025-71111/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-71111
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-71111
- OSV: https://osv.dev/vulnerability/CVE-2025-71111

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-71111/
Summaries are generated and may contain mistakes; the official description above is the record.