CVE-2025-21641

Local kernel crash via null nsproxy dereference

Published Jan 19, 2025 · Updated May 11, 2026

NULL pointer dereference in Linux 6.12 allows local users to crash the kernel through the MPTCP blackhole timeout sysctl. The MPTCP sysctl handler derives its network namespace through current->nsproxy, which can be NULL while the accessing task exits, instead of recovering the per-network structure from the table data. Low-privileged local access and the task-exit race are required; successful triggering produces a kernel Oops and interrupts the host.

CVSS severity5.5
Medium
EPSS probability0.18%
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 6.12 allows local users to crash the kernel through the MPTCP blackhole timeout sysctl. The MPTCP sysctl handler derives its network namespace through current->nsproxy, which can be NULL while the accessing task exits, instead of recovering the per-network structure from the table data. Low-privileged local access and the task-exit race are required; successful triggering produces a kernel Oops and interrupts the host.

The record

CVE
CVE-2025-21641
Published
Jan 19, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-476, 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=27069e7cb3d1cea9377069266acf19b9cc5ad0ae <4c74fbdc5ab95b13945be01e6065940b68222db7
  2. Affected versionversion=27069e7cb3d1cea9377069266acf19b9cc5ad0ae <92cf7a51bdae24a32c592adcdd59a773ae149289
  3. Affected versionversion=6.12

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=27069e7cb3d1cea9377069266acf19b9cc5ad0ae <4c74fbdc5ab95b13945be01e6065940b68222db7; version=27069e7cb3d1cea9377069266acf19b9cc5ad0ae <92cf7a51bdae24a32c592adcdd59a773ae149289; version=6.12

Published CVSS scores

5.5CISA-ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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

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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
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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