CVE-2025-21921

Kernel crash via NULL ethtool request attributes

Published Apr 1, 2025 · Updated May 11, 2026

NULL pointer dereference in Linux kernel ethtool netlink code allows local users to crash the kernel through a PLCA set operation. In ethnl_req_get_phydev(), the notification path dereferences the request-attribute table even though that table is NULL after the operation. The path requires local low-privileged access and a PLCA notification for a missing PHY device; the reported consequence is loss of availability only.

CVSS severity5.5
Medium
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in Linux kernel ethtool netlink code allows local users to crash the kernel through a PLCA set operation. In ethnl_req_get_phydev(), the notification path dereferences the request-attribute table even though that table is NULL after the operation. The path requires local low-privileged access and a PLCA notification for a missing PHY device; the reported consequence is loss of availability only.

The record

CVE
CVE-2025-21921
Published
Apr 1, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-476, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 1, 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=6.12
  2. Affected versionversion=c15e065b46dc4e19837275b826c1960d55564abd <1f458fa42c29144cef280e05bc49fc21b873d897
  3. Affected versionversion=c15e065b46dc4e19837275b826c1960d55564abd <637399bf7e77797811adf340090b561a8f9d1213
  4. Affected versionversion=c15e065b46dc4e19837275b826c1960d55564abd <639c70352958735addbba5ae7dd65985da96e061

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.12; version=c15e065b46dc4e19837275b826c1960d55564abd <1f458fa42c29144cef280e05bc49fc21b873d897; version=c15e065b46dc4e19837275b826c1960d55564abd <637399bf7e77797811adf340090b561a8f9d1213; version=c15e065b46dc4e19837275b826c1960d55564abd <639c70352958735addbba5ae7dd65985da96e061

Published CVSS scores

5.5NIST NVDCVSS: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-476NULL Pointer Dereference
T1499.004Application or System Exploitation

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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