CVE-2025-21666

Local system crash via de-assigned vsock transport

Published Jan 31, 2025 · Updated May 12, 2026

NULL pointer dereference in Linux kernel vsock allows local users to crash affected systems through a de-assigned transport. In net/vmw_vsock/af_vsock.c, the data and space helpers dereference the transport after it has been removed from the socket instead of returning zero. Low-privileged local access is required, and the documented consequence is an availability-only kernel crash rather than data access or modification.

CVSS severity5.5
Medium
EPSS probability0.22%
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 vsock allows local users to crash affected systems through a de-assigned transport. In net/vmw_vsock/af_vsock.c, the data and space helpers dereference the transport after it has been removed from the socket instead of returning zero. Low-privileged local access is required, and the documented consequence is an availability-only kernel crash rather than data access or modification.

The record

CVE
CVE-2025-21666
Published
Jan 31, 2025
Updated
May 12, 2026
Vendor
Siemens
Product
SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
Classifications
CWE-476, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 31, 2025CVE publishedPublication date reported by the CVE source.
  2. May 12, 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=0 <*

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Siemens · SIMATIC S7-1500 TM MFP - GNU/Linux subsystemversion=0 <*
The Linux Kernel Organization · Linuxversion=5.5; version=c0cfa2d8a788fcf45df5bf4070ab2474c88d543a <91751e248256efc111e52e15115840c35d85abaf; version=c0cfa2d8a788fcf45df5bf4070ab2474c88d543a <9e5fed46ccd2c34c5fa5a9c8825ce4823fdc853e; version=c0cfa2d8a788fcf45df5bf4070ab2474c88d543a <b52e50dd4fabd12944172bd486a4f4853b7f74dd; version=c0cfa2d8a788fcf45df5bf4070ab2474c88d543a <bc9c49341f9728c31fe248c5fbba32d2e81a092b; version=c0cfa2d8a788fcf45df5bf4070ab2474c88d543a <c23d1d4f8efefb72258e9cedce29de10d057f8ca; version=c0cfa2d8a788fcf45df5bf4070ab2474c88d543a <daeac89cdb03d30028186f5ff7dc26ec8fa843e7

Published CVSS scores

5.5SiemensCVSS: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.

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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
T1499.004Endpoint Denial of Service: Application 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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