CVE-2025-38700 Siemens CVE debrief

Who should care

Operators and administrators responsible for Siemens SIMATIC CN 4100 systems, especially environments using Linux kernel iSCSI/iSER paths or other storage workloads that rely on libiscsi. ICS teams should also care because the failure mode is a device or host crash/panic rather than a benign error.

Technical summary

The source advisory describes a logic flaw in scsi: libiscsi where iscsi_conn->dd_data is set unconditionally even when dd_size is zero. If ib_fast_reg_mr allocation fails during iSER setup, no buffer is allocated, but teardown later follows the invalid pointer and faults in swake_up_locked/complete during iscsi_iser_conn_stop. The result is a panic path triggered by connection stop handling. The advisory’s 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. The primary operational risk is kernel panic and service interruption on affected systems. Remediation is available and should be prioritized where the advisory applies.

Recommended defensive actions

• Update to Siemens V5.0 or later, as listed in the advisory remediation.
• Verify whether any affected SIMATIC CN 4100 deployments use the impacted Linux kernel storage path or iSER-related functionality.
• Review system hardening and access controls for storage-management paths; CISA ICS recommended practices are referenced in the advisory.
• Monitor affected hosts for unexpected kernel panics or repeated connection teardown failures until remediation is complete.
• Treat the Siemens product mapping as advisory-provided metadata and confirm exposure in your own asset inventory before scheduling maintenance.

Evidence notes

This debrief is based on the CISA CSAF advisory ICSA-26-134-10 and its republished Siemens ProductCERT SSA-032379 content, both dated 2026-05-12 with a CISA republication on 2026-05-14. The advisory text states that an ib_fast_reg_mr allocation failure during iSER setup can leave iscsi_conn->dd_data initialized without allocated memory, leading to an invalid pointer dereference during connection teardown and a kernel panic. The source also lists the remediation as updating to V5.0 or later. The product mapping in the supplied source is marked low confidence and should be reviewed in local inventory.

Sources and references

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.