CVE-2025-21664

Kernel crash via RCU-unsafe thin-device list lookup

Published Jan 21, 2025 · Updated Aug 5, 2026

Race condition in the dm-thin driver in Linux allows local users to crash the kernel during concurrent thin-device I/O and teardown. The get_first_thin() function separately checks list_empty() and then reads the first RCU list entry, allowing thin_dtr() to remove the last entry between those reads and leave a self-referential list head interpreted as thin_c. Triggering the fault requires local access to a thin volume and concurrent device teardown; the documented consequence is a general-protection fault and system crash.

CVSS severity7.8
High
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Race condition in the dm-thin driver in Linux allows local users to crash the kernel during concurrent thin-device I/O and teardown. The get_first_thin() function separately checks list_empty() and then reads the first RCU list entry, allowing thin_dtr() to remove the last entry between those reads and leave a self-referential list head interpreted as thin_c. Triggering the fault requires local access to a thin volume and concurrent device teardown; the documented consequence is a general-protection fault and system crash.

The record

CVE
CVE-2025-21664
Published
Jan 21, 2025
Updated
Aug 5, 2026
Vendor
Siemens
Product
SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
Classifications
CWE-20, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 21, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 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=3.15; version=b10ebd34cccae1b431caf1be54919aede2be7cbe <12771050b6d059eea096993bf2001da9da9fddff; version=b10ebd34cccae1b431caf1be54919aede2be7cbe <6b305e98de0d225ccebfb225730a9f560d28ecb0; version=b10ebd34cccae1b431caf1be54919aede2be7cbe <802666a40c71a23542c43a3f87e3a2d0f4e8fe45; version=b10ebd34cccae1b431caf1be54919aede2be7cbe <80f130bfad1dab93b95683fc39b87235682b8f72; version=b10ebd34cccae1b431caf1be54919aede2be7cbe <cbd0d5ecfa390ac29c5380200147d09c381b2ac6; version=b10ebd34cccae1b431caf1be54919aede2be7cbe <cd30a3960433ec2db94b3689752fa3c5df44d649; version=b10ebd34cccae1b431caf1be54919aede2be7cbe <ec037fe8c0d0f6140e3d8a49c7b29cb5582160b8

Published CVSS scores

5.5Siemens ProductCERTCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
7.8Linux Kernel CNACVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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-20Improper Input Validation
T1499.004Application or System Exploitation

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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