CVE-2025-38100 Siemens CVE debrief

Who should care

Siemens SIMATIC S7-1500 operators, OT/ICS administrators, and anyone responsible for systems that expose the affected GNU/Linux subsystem or local shell access. It is most relevant where local users, maintenance workflows, or embedded Linux components can reach the kernel paths described in the advisory.

Technical summary

The supplied description says io_bitmap_exit() can call task_update_io_bitmap() in a way that reaches tss_update_io_bitmap() on the current task even when the current task has TIF_IO_BITMAP set but no bitmap installed. That inconsistent state can crash the kernel with a NULL pointer dereference. The described remediation is to avoid updating I/O bitmap state for a non-current task during failed-fork cleanup, clear TIF_IO_BITMAP in copy_thread(), and warn if tss_update_io_bitmap() is called with inconsistent state. The published CVSS vector is AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

Defensive priority

Medium. The record indicates a local, availability-only issue with no confidentiality or integrity impact, but in OT environments even a local kernel crash can be operationally significant. Prioritize exposure review and access restriction while awaiting vendor guidance or a fix.

Recommended defensive actions

• Identify whether any affected SIMATIC S7-1500 CPU family product listed in the advisory is in use.
• Review whether the GNU/Linux subsystem or interactive shell access is exposed to more users than necessary.
• Restrict shell and local administrative access to trusted personnel only, as recommended in the advisory.
• Limit execution to trusted software sources and maintenance workflows.
• Monitor affected systems for unexpected kernel crashes, watchdog resets, or instability consistent with a denial-of-service condition.
• Track Siemens/CISA advisory updates for a vendor fix or additional mitigation guidance.

Evidence notes

The supplied source item is CISA CSAF advisory ICSA-25-162-05, published 2025-06-10 and most recently updated/republished 2026-05-14. The advisory names five affected Siemens SIMATIC S7-1500 CPU family products and states that no fix is currently available in the provided remediations. The vulnerability description explicitly attributes the issue to TIF_IO_BITMAP inconsistency causing a NULL pointer dereference in tss_update_io_bitmap(), and the supplied CVSS vector is AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

Official resources