PatchSiren

PatchSiren cyber security CVE debrief

CVE-2025-21787 Siemens CVE debrief

CVE-2025-21787 is a MEDIUM severity vulnerability (CVSS 5.5) affecting the Siemens SIMATIC S7-1500 TM MFP GNU/Linux subsystem. The issue involves improper validation of TEAM_OPTION_TYPE_STRING, which could lead to a denial-of-service condition. The vulnerability requires local access with low privileges and no user interaction, making it exploitable by authenticated users with shell access to the GNU/Linux subsystem. No patch is currently available; Siemens and CISA recommend restricting interactive shell access to trusted personnel only and ensuring only applications from trusted sources are built and executed. The vulnerability was disclosed in CISA advisory ICSA-24-102-01 on April 9, 2024, with the advisory receiving multiple updates through September 2025 to include additional related CVEs.

Vendor
Siemens
Product
SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
CVSS
MEDIUM 5.5
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 controllers in industrial environments, particularly those utilizing the GNU/Linux subsystem for custom applications. OT security teams, plant engineers, and asset owners in manufacturing, process control, and critical infrastructure sectors should prioritize access controls given the absence of a security patch.

Technical summary

The vulnerability exists in the GNU/Linux subsystem of the Siemens SIMATIC S7-1500 TM MFP industrial controller. Insufficient validation of TEAM_OPTION_TYPE_STRING parameters can be exploited by a locally authenticated attacker with low privileges to cause a denial-of-service condition. The attack requires no user interaction and has no confidentiality or integrity impact, but results in high availability impact. The CVSS 3.1 vector is AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

Defensive priority

medium

Recommended defensive actions

  • Restrict interactive shell access to the GNU/Linux subsystem to trusted personnel only
  • Only build and run applications from trusted sources
  • Monitor for future Siemens security advisories for patch availability
  • Apply defense-in-depth strategies for industrial control systems per CISA guidance

Evidence notes

CVE published 2024-04-09 per CISA CSAF source ICSA-24-102-01. Advisory modified 2026-05-14. CVSS vector AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H indicates local attack vector with availability impact. No fix available per remediation data.

Sources and references

Verified primary and authoritative sources

  • CVE-2025-21787 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2025-21787

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

  • CVE-2025-21787 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2025-21787

    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.