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PatchSiren cyber security CVE debrief

CVE-2025-21664 Siemens CVE debrief

This CVE addresses a race condition in the Linux kernel's Device Mapper (dm) thin provisioning subsystem. The vulnerability exists in the `get_first_thin` function, which previously used a non-RCU-safe list operation that could lead to use-after-free conditions during concurrent access. The fix converts this to use RCU-safe list traversal primitives, preventing potential system instability or denial of service when the thin provisioning target is under heavy concurrent load. The vulnerability is local in nature, requiring low privileges and no user interaction, but can result in high availability impact through system crashes or memory corruption.

Vendor
Siemens
Product
SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
CVSS
HIGH 7.8
CISA KEV
Not listed in stored evidence
Original CVE published
2025-01-21
Original CVE updated
2026-07-30
Advisory published
2025-01-21
Advisory updated
2026-07-30

Who should care

Organizations running Siemens SIMATIC S7-1500 TM MFP with the GNU/Linux subsystem enabled, particularly in industrial control environments where device availability is critical. System administrators maintaining Linux-based embedded systems using dm-thin provisioning should also assess exposure.

Technical summary

The Device Mapper thin provisioning target in the Linux kernel contains a race condition where `get_first_thin` uses non-RCU-safe list operations. Under concurrent access, this can trigger use-after-free conditions leading to kernel crashes or memory corruption. The vulnerability is exploitable locally with low privileges and requires no user interaction. The fix implements proper RCU list traversal to ensure safe concurrent access patterns.

Defensive priority

medium

Recommended defensive actions

  • Limit access to the interactive shell of the additional GNU/Linux subsystem to trusted personnel only
  • Only build and run applications from trusted sources
  • Monitor for vendor security updates as no fix is currently available
  • Apply defense-in-depth strategies for industrial control systems per CISA guidance

Evidence notes

CVE published 2024-04-09 per CISA CSAF advisory ICSA-24-102-01. Advisory last modified 2026-05-14. This CVE was added to the advisory in Additional Release 6 (2025-06-10). CVSS 3.1 vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H. CWE-20 (Improper Input Validation) referenced.

Sources and references

Verified primary and authoritative sources

  • CVE-2025-21664 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2025-21664

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2025-21664 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2025-21664

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Source item URL

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/cisagov/CSAF/develop/csaf_files/OT/white/2024/icsa-24-102-01.json

    cisa_csaf

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/csaf/ssa-265688.json

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/html/ssa-265688.html

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/news-events/ics-advisories/icsa-24-102-01

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/news-events/ics-alerts/ics-alert-10-301-01

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/resources-tools/resources/ics-recommended-practices

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/topics/industrial-control-systems

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/sites/default/files/recommended_practices/NCCIC_ICS-CERT_Defense_in_Depth_2016_S508C.pdf

    Reference

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.