CVE-2025-21634

Local denial of service via cpuset removal race

Published Jan 19, 2025 · Updated May 11, 2026

Improper locking in the Linux kernel cpuset subsystem allows local users to cause denial of service through concurrent cgroup operations. cpuset_write_resmask() breaks kernfs active protection while writing cpuset.cpus, so concurrent cgroup removal leaves an unexpected active-reference count and triggers a kernel warning. The race requires local privileges sufficient to modify and remove a cpuset cgroup; its documented consequence is availability loss rather than data access or modification.

CVSS severity5.5
Medium
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper locking in the Linux kernel cpuset subsystem allows local users to cause denial of service through concurrent cgroup operations. cpuset_write_resmask() breaks kernfs active protection while writing cpuset.cpus, so concurrent cgroup removal leaves an unexpected active-reference count and triggers a kernel warning. The race requires local privileges sufficient to modify and remove a cpuset cgroup; its documented consequence is availability loss rather than data access or modification.

The record

CVE
CVE-2025-21634
Published
Jan 19, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-667, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 19, 2025CVE publishedPublication date reported by the CVE source.
  2. May 11, 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=3.16
  2. Affected versionversion=76bb5ab8f6e3e7bebdcefec4146ff305e7d0b465 <11cb1d643a74665a4e14749414f48f82cbc15c64
  3. Affected versionversion=76bb5ab8f6e3e7bebdcefec4146ff305e7d0b465 <3cb97a927fffe443e1e7e8eddbfebfdb062e86ed

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=3.16; version=76bb5ab8f6e3e7bebdcefec4146ff305e7d0b465 <11cb1d643a74665a4e14749414f48f82cbc15c64; version=76bb5ab8f6e3e7bebdcefec4146ff305e7d0b465 <3cb97a927fffe443e1e7e8eddbfebfdb062e86ed

Published CVSS scores

5.5CISA ADPCVSS:3.1/AV:L/AC:L/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-667Improper Locking
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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