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PatchSiren cyber security CVE debrief

CVE-2025-38063 Siemens CVE debrief

CVE-2025-38063 is a Linux kernel device-mapper issue that can cause unnecessary I/O throttling when a flush request is processed. Siemens’ advisory maps the issue to several SIMATIC S7-1500 CPU models with an additional GNU/Linux subsystem, and the source material notes that no fix was available at publication time.

Vendor
Siemens
Product
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)
CVSS
MEDIUM 5.5
CISA KEV
Not listed in stored evidence
Original CVE published
2025-06-10
Original CVE updated
2026-05-14
Advisory published
2025-06-10
Advisory updated
2026-05-14

Who should care

Operators, maintainers, and OT security teams responsible for the affected Siemens SIMATIC S7-1500 CPU models, especially environments that rely on the GNU/Linux subsystem or storage paths that issue flush-heavy I/O.

Technical summary

The underlying kernel problem is in dm flush handling: when a bio with REQ_PREFLUSH is submitted, __send_empty_flush() creates a flush_bio marked REQ_OP_WRITE | REQ_PREFLUSH | REQ_SYNC. That combination causes the flush_bio to be throttled by wbt_wait(), which can impose an unintended availability and performance penalty. The advisory’s CVSS vector reflects a local, low-complexity issue with high availability impact and no confidentiality or integrity impact.

Defensive priority

Medium; elevate operational priority if the affected device relies on the GNU/Linux subsystem or performance-sensitive storage workloads.

Recommended defensive actions

  • Confirm whether any affected Siemens SIMATIC S7-1500 CPU models are in use and whether the GNU/Linux subsystem is enabled.
  • Treat this as an availability and performance issue; validate whether I/O throttling could affect control or maintenance workloads.
  • Apply Siemens and CISA updates when a vendor fix or revised mitigation becomes available.
  • Until a fix exists, restrict shell access to trusted personnel only.
  • Only build and run applications from trusted sources on the affected subsystem.

Evidence notes

CISA’s CSAF advisory for ICSA-25-162-05 published on 2025-06-10 and last updated on 2026-05-14 links CVE-2025-38063 to Siemens SIMATIC S7-1500 CPU family products. The source description states that the Linux kernel dm path can generate a flush_bio that is throttled by wbt_wait() when REQ_PREFLUSH is submitted, and the remediation section states that no fix was available at the time reflected in the source.

Sources and references

Verified primary and authoritative sources

  • CVE-2025-38063 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2025-38063

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

  • CVE-2025-38063 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2025-38063

    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/2025/icsa-25-162-05.json

    cisa_csaf

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/csaf/ssa-082556.json

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/html/ssa-082556.html

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/news-events/ics-advisories/icsa-25-162-05

    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.