CVE-2025-38708 Cert Portal CVE debrief

Who should care

Teams responsible for Siemens SIMATIC CN 4100 systems covered by the advisory, plus administrators of DRBD-based Linux deployments that may use two-primaries or related write-conflict handling. This is most relevant where kernel stability is operationally important.

Technical summary

The advisory text says DRBD’s two-primaries mode tries to reconcile concurrent writes and that the vulnerable code path handled "superseeded" writes without a required kref_get. That missing reference increment can allow a device object to be destroyed too early, creating a use-after-free condition and resulting in kernel crashes. The source corpus gives CVSS 3.1 7.8/High with vector AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H, indicating local access and privileges are required but impact can be severe.

Defensive priority

High. Prioritize remediation for any confirmed affected Siemens SIMATIC CN 4100 deployment or DRBD-based Linux system in scope, especially where kernel crashes would affect availability or safety.

Recommended defensive actions

• Confirm whether your environment includes Siemens SIMATIC CN 4100 systems covered by ICSA-26-134-10 or DRBD-based Linux kernels using the vulnerable write-conflict path.
• Apply the vendor remediation: update to V5.0 or later, per the Siemens advisory.
• Schedule remediation through normal maintenance windows, but treat confirmed exposure as a high-priority stability issue.
• Review operational dependencies on concurrent-write behavior; the advisory states this path is rarely used in normal clustered storage or live-migration workflows, but test or unusual configurations may still be at risk.
• Track the Siemens and CISA advisory revisions for any clarification or additional affected-product details.

Evidence notes

The supplied CSAF source states: "In the Linux kernel, the following vulnerability has been resolved: drbd: add missing kref_get in handle_write_conflicts," and describes a use-after-free leading to kernel crashes. It also lists Siemens SIMATIC CN 4100 vers:intdot/<5.0, a CVSS 3.1 score of 7.8 (High), and remediation to update to V5.0 or later. The source vendor mapping is marked low-confidence/needs review, so product applicability should be verified against the Siemens bulletin and affected-device inventory. Not listed in CISA KEV.

Official resources