CVE-2025-71111

Service interruption via fan-divisor TOCTOU race

Published Jan 14, 2026 · Updated Jan 14, 2026

A TOCTOU race in the Linux Kernel w83791d hwmon driver allows local users to interrupt system operation through concurrent fan access. The FAN_FROM_REG macro reevaluates shared fan-divisor data without a lock, while store_fan_div calculates the minimum limit before acquiring update_lock, so concurrent reads and writes can supply an inconsistent zero divisor. Exploitation requires low-privileged local access, a loaded w83791d driver, and precise race timing; the bounded consequence is a divide-by-zero service interruption.

CVSS severity4.7
Medium
EPSS probability0.10%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A TOCTOU race in the Linux Kernel w83791d hwmon driver allows local users to interrupt system operation through concurrent fan access. The FAN_FROM_REG macro reevaluates shared fan-divisor data without a lock, while store_fan_div calculates the minimum limit before acquiring update_lock, so concurrent reads and writes can supply an inconsistent zero divisor. Exploitation requires low-privileged local access, a loaded w83791d driver, and precise race timing; the bounded consequence is a divide-by-zero service interruption.

The record

CVE
CVE-2025-71111
Published
Jan 14, 2026
Updated
Jan 14, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-367, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 14, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 14, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.6.18
  2. Affected versionversion=9873964d6eb24bd0205394f9b791de9eddbcb855 <670d7ef945d3a84683594429aea6ab2cdfa5ceb4
  3. Affected versionversion=9873964d6eb24bd0205394f9b791de9eddbcb855 <a9fb6e8835a22f5796c1182ed612daed3fd273af
  4. Affected versionversion=9873964d6eb24bd0205394f9b791de9eddbcb855 <c8cf0c2bdcccc6634b6915ff793b844e12436680
  5. Affected versionversion=9873964d6eb24bd0205394f9b791de9eddbcb855 <f2b579a0c37c0df19603d719894a942a295f634a
  6. Affected versionversion=9873964d6eb24bd0205394f9b791de9eddbcb855 <f94800fbc26ccf7c81eb791707b038a57aa39a18

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=2.6.18; version=9873964d6eb24bd0205394f9b791de9eddbcb855 <670d7ef945d3a84683594429aea6ab2cdfa5ceb4; version=9873964d6eb24bd0205394f9b791de9eddbcb855 <a9fb6e8835a22f5796c1182ed612daed3fd273af; version=9873964d6eb24bd0205394f9b791de9eddbcb855 <c8cf0c2bdcccc6634b6915ff793b844e12436680; version=9873964d6eb24bd0205394f9b791de9eddbcb855 <f2b579a0c37c0df19603d719894a942a295f634a; version=9873964d6eb24bd0205394f9b791de9eddbcb855 <f94800fbc26ccf7c81eb791707b038a57aa39a18

Published CVSS scores

4.7NIST NVDCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
4.7Red HatCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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