CVE-2021-3712 Siemens CVE debrief

Who should care

Operators and maintainers of the affected Siemens SCALANCE wireless devices, OT/ICS security teams, and any application owners that rely on OpenSSL to print or process ASN.1 data from directly constructed ASN1_STRING objects.

Technical summary

OpenSSL’s ASN.1 printing and related routines can read past the end of an ASN1_STRING buffer when the code expects a terminating NUL byte that is not guaranteed for directly constructed strings or strings created with ASN1_STRING_set0(). The advisory notes that this can affect ASN.1 printing, certificate name-constraint processing, X509_get1_email(), X509_REQ_get1_email(), and X509_get1_ocsp(). The corpus states that affected OpenSSL releases were 1.1.1 through 1.1.1k and 1.0.2 through 1.0.2y, with fixes in 1.1.1l and 1.0.2za; Siemens remediates the impacted SCALANCE product set by moving to V6.6.0 or later.

Defensive priority

High for affected SCALANCE deployments. Prioritize remediation because the flaw can lead to denial of service and potential memory disclosure, and the advisory maps it to multiple industrial wireless products.

Recommended defensive actions

• Confirm whether any listed Siemens SCALANCE models are deployed in your environment and whether they are running versions earlier than V6.6.0.
• Apply Siemens’ remediation to update affected devices to V6.6.0 or later using the linked ProductCERT guidance.
• Treat the advisory as a memory-safety exposure in OpenSSL-dependent workflows and verify whether any local applications directly construct ASN1_STRING objects or use ASN1_STRING_set0().
• Reduce operational exposure for affected devices by segmenting OT networks and limiting unnecessary access to management interfaces.
• Monitor for unexpected crashes or abnormal behavior in systems that process certificates or ASN.1 data until remediation is complete.

Evidence notes

The source corpus is a CISA CSAF republication of Siemens ProductCERT advisory SSA-019200 (ICSA-26-111-07), first published on 2026-04-14 and republished on 2026-04-21. The advisory text explicitly describes a read buffer overrun in OpenSSL ASN.1 handling, cites potential crash and private-memory disclosure, and lists the Siemens SCALANCE product set plus the V6.6.0-or-later fix. The vendor mapping in the supplied metadata is marked low confidence/needs review, so the product association should be treated as advisory-backed but not independently validated here.

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.