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CVE-2025-21858 Siemens CVE debrief

CVE-2025-21858 is a use-after-free vulnerability in the Linux kernel's Generic Network Virtualization Encapsulation (GENEVE) driver, specifically within the `geneve_find_dev()` function. The vulnerability was published on April 9, 2024, and last modified on May 14, 2026. Siemens has identified this vulnerability as affecting the GNU/Linux subsystem of the SIMATIC S7-1500 TM MFP industrial control system product. The vulnerability carries a CVSS 3.1 score of 7.8 (HIGH severity) with a vector of AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H, indicating that a local attacker with low privileges can achieve high impacts on confidentiality, integrity, and availability without user interaction. Use-after-free vulnerabilities in kernel networking drivers can potentially lead to privilege escalation, system crashes, or code execution. The advisory notes that currently no fix is available for this product.

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
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 systems with the GNU/Linux subsystem enabled, particularly in critical infrastructure, manufacturing, and process control environments. Security teams responsible for industrial control system hardening, network architects designing OT/IT segmentation, and system administrators managing user access to embedded Linux environments on PLCs should prioritize assessment and mitigation. The lack of available patches makes this especially important for organizations with strict patching timelines or regulatory compliance requirements.

Technical summary

This vulnerability exists in the GENEVE (Generic Network Virtualization Encapsulation) tunneling driver's device lookup function. GENEVE is a network virtualization overlay protocol used in cloud and data center environments. The use-after-free condition in `geneve_find_dev()` suggests that a race condition or improper reference counting could allow an attacker to trigger memory corruption. On the affected Siemens product, this resides in the GNU/Linux subsystem, which provides extended functionality beyond the standard PLC runtime. The local attack vector indicates that an attacker must already have access to the Linux environment, making this particularly relevant for multi-user or compromised-application scenarios on the industrial device.

Defensive priority

HIGH

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 future security updates from Siemens for patch availability
  • Apply defense-in-depth strategies for industrial control systems per CISA guidance
  • Review and implement ICS-CERT recommended practices for network segmentation and access control

Evidence notes

The vulnerability description 'geneve: Fix use-after-free in geneve_find_dev()' indicates this is a Linux kernel networking driver issue. The CVSS vector confirms local attack vector with low attack complexity and low privileges required, but with high impact across all three security dimensions. The affected product is specifically the GNU/Linux subsystem of Siemens SIMATIC S7-1500 TM MFP, an industrial control system platform. The advisory explicitly states 'Currently no fix is available' as of the source publication.

Sources and references

Verified primary and authoritative sources

  • CVE-2025-21858 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2025-21858

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

  • CVE-2025-21858 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2025-21858

    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.