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PatchSiren cyber security CVE debrief

CVE-2025-38725 Siemens CVE debrief

CVE-2025-38725 is a Linux kernel vulnerability described in the Siemens/CISA advisory set. The issue is in the ax88772 MDIO bus handling for usb net devices: without a phy_mask, the driver may create extra PHY devices, and only one binds to the network PHY driver. During suspend/resume, non-main PHY devices can trigger a NULL pointer dereference in the PHY state machine. The supplied remediation is to update to V5.0 or later.

Vendor
Siemens
Product
SIMATIC CN 4100
CVSS
HIGH 7
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

Administrators and operators responsible for the affected Siemens SIMATIC CN 4100 systems listed in the advisory, especially where Linux kernel USB network adapters or suspend/resume behavior are in use. Security teams that manage OT/industrial systems should also review the advisory scope and firmware version mapping.

Technical summary

The advisory describes a missing phy_mask on the ax88772 MDIO bus in the Linux kernel’s asix_devices path. The driver can instantiate up to 32 MDIO PHY devices across address range 0x00-0x1f, but only the primary PHY binds to the net PHY driver. When the system suspends or resumes, phy_polling_mode() in phy_state_machine() may dereference phydev->drv for non-main PHY devices, which can lead to a NULL pointer dereference. The supplied CVSS vector is CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H.

Defensive priority

High for any system matching the advisory’s affected product/version scope. Confirm exposure, then apply the vendor update path to V5.0 or later as soon as practical.

Recommended defensive actions

  • Update to V5.0 or later version, as stated in the remediation guidance.
  • Verify whether the deployed Siemens SIMATIC CN 4100 system is within the advisory’s affected version range before scheduling maintenance.
  • Review the CISA and Siemens advisory links for any additional vendor guidance or clarifications.
  • Track suspend/resume behavior on affected devices during change windows so operational impact can be assessed before and after remediation.

Evidence notes

Source material published on 2026-05-12 and republished on 2026-05-14. The description attributes the bug to a Linux kernel USB network driver issue and the remediation to a vendor update. The supplied advisory metadata also marks the vendor/product mapping as low confidence and needs review, so the affected-product scope should be interpreted cautiously.

Sources and references

Verified primary and authoritative sources

  • CVE-2025-38725 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2025-38725

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

  • CVE-2025-38725 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2025-38725

    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.