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PatchSiren cyber security CVE debrief

CVE-2025-21704 Siemens CVE debrief

A vulnerability in the USB CDC-ACM driver of the Linux kernel, affecting Siemens SIMATIC S7-1500 TM MFP industrial control systems. The flaw involves improper validation of control transfer buffer sizes, which could allow a local attacker with high privileges to cause denial of service conditions. The vulnerability was disclosed in April 2024 and affects the GNU/Linux subsystem of this industrial automation platform.

Vendor
Siemens
Product
SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
CVSS
MEDIUM 4.4
CISA KEV
Not listed in stored evidence
Original CVE published
2024-04-09
Original CVE updated
2026-05-14
Advisory published
2024-04-09
Advisory updated
2026-05-14

Who should care

Organizations operating Siemens SIMATIC S7-1500 TM MFP industrial control systems with the GNU/Linux subsystem enabled. This includes manufacturing facilities, critical infrastructure operators, and industrial automation environments where these programmable logic controllers are deployed. System administrators and OT security teams responsible for securing industrial control system assets should prioritize access controls given the absence of an available patch.

Technical summary

The vulnerability exists in the USB Communications Device Class Abstract Control Model (CDC-ACM) driver within the Linux kernel. The driver fails to properly validate the size of control transfer buffers before accessing them. This improper input validation (CWE-20) could be exploited by a local attacker with high privileges to trigger denial of service conditions. The attack requires local access with high privileges, has low attack complexity, and results in high availability impact with no confidentiality or integrity impact per the CVSS 3.1 vector.

Defensive priority

medium

Recommended defensive actions

  • Restrict interactive shell access to the GNU/Linux subsystem to trusted personnel only
  • Implement application whitelisting to ensure only trusted applications are built and executed
  • Monitor for anomalous USB device connections to affected systems
  • Apply defense-in-depth strategies per CISA ICS recommended practices
  • Subscribe to Siemens ProductCERT security advisories for patch availability updates

Evidence notes

CISA ICS advisory ICSA-24-102-01 documents this vulnerability in Siemens SIMATIC S7-1500 TM MFP systems. The advisory was initially published on April 9, 2024, and has undergone multiple revisions through September 2025 to incorporate additional CVEs. Siemens has confirmed no patch is currently available.

Sources and references

Verified primary and authoritative sources

  • CVE-2025-21704 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2025-21704

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

  • CVE-2025-21704 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2025-21704

    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.