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PatchSiren cyber security CVE debrief

CVE-2025-39710 Siemens CVE debrief

CVE-2025-39710 is a medium-severity bounds-checking issue described in the supplied advisory corpus as a packet-size validation flaw in the Linux kernel media: venus path. The advisory text says packet size read from shared memory was not being checked against the number of available words, creating a risk of out-of-bounds memory access. In the supplied product mapping, Siemens SIMATIC CN 4100 versions prior to 5.0 are listed as affected, with a fix to update to V5.0 or later. The provided CVSS vector indicates local access and elevated privileges are required, with the main impact being availability.

Vendor
Siemens
Product
SIMATIC CN 4100
CVSS
MEDIUM 5.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-12
Original CVE updated
2026-05-14
Advisory published
2026-05-12
Advisory updated
2026-05-14

Who should care

OT/ICS operators and asset owners running Siemens SIMATIC CN 4100 versions earlier than 5.0, along with administrators and maintenance teams responsible for patching embedded Linux-based components and validating vendor advisories.

Technical summary

The issue is a missing bounds check on a packet size value read from shared memory after the packet header is parsed. If the size exceeds the number of available words, the driver could process an invalid length and risk out-of-bounds memory access. The supplied corpus associates this with Siemens SIMATIC CN 4100 <5.0 and recommends updating to V5.0 or later, but the corpus also contains Linux kernel media: venus wording, so the product attribution should be reviewed carefully.

Defensive priority

Medium. Plan remediation in the next maintenance window, sooner for high-value or safety-relevant deployments, because a vendor fix is available and the issue affects availability.

Recommended defensive actions

  • Inventory Siemens SIMATIC CN 4100 deployments and confirm whether any are running versions earlier than V5.0.
  • Apply the vendor-recommended update to V5.0 or later during a controlled maintenance window.
  • Validate the update in a test environment first and confirm rollback options for operational continuity.
  • Follow Siemens and CISA advisory updates for any additional mitigation or clarification tied to this CVE.
  • Use defense-in-depth controls from the CISA ICS guidance to limit administrative access and reduce exposure to local compromise paths.

Evidence notes

The timing and remediation guidance are taken from the supplied CISA CSAF advisory ICSA-26-134-10, published 2026-05-12 and republished 2026-05-14. The corpus links the vulnerability description to a Linux kernel media: venus packet-size check and also maps it to Siemens SIMATIC CN 4100 <5.0; because those signals do not fully align, the vendor/product attribution should be treated as low-confidence and verified against the Siemens ProductCERT advisory.

Sources and references

Verified primary and authoritative sources

  • CVE-2025-39710 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2025-39710

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

  • CVE-2025-39710 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2025-39710

    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/2026/icsa-26-134-10.json

    cisa_csaf

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/csaf/ssa-032379.json

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/html/ssa-032379.html

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/news-events/ics-advisories/icsa-26-134-10

    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.