CVE-2023-32737 Siemens CVE debrief

Who should care

Industrial control system security teams, OT security architects, Siemens TIA Portal administrators, PLC programmers and engineers, manufacturing security operations centers, critical infrastructure asset owners using SIMATIC STEP 7 Safety for safety instrumented system programming

Technical summary

The vulnerability exists in the deserialization path of SIMATIC STEP 7 Safety V18 where user-controllable input is passed to the .NET BinaryFormatter without adequate restrictions. BinaryFormatter is a known-dangerous serialization mechanism in .NET that performs full type deserialization, enabling attackers to craft malicious payloads that instantiate arbitrary types during deserialization. The type confusion arises when the deserializer instantiates attacker-controlled types that chain into dangerous operations. Successful exploitation yields arbitrary code execution within the security context of the STEP 7 Safety application. The CVSS 3.1 vector (AV:L/AC:H/PR:H/UI:R/S:U/C:H/I:H/A:H/E:P/RL:O/RC:C) indicates local attack vector, high attack complexity, high privileges required, and user interaction required—suggesting exploitation likely requires social engineering or insider access to introduce malicious project files or MMC card content.

Defensive priority

high

Recommended defensive actions

• Apply vendor fix: Update SIMATIC STEP 7 Safety V18 to Update 2 or later version
• Implement operational control: Avoid uploading PLC software from untrusted devices or MMC cards
• Review engineering workstation security: Restrict physical and logical access to STEP 7 installations
• Audit project file handling: Validate source integrity of all imported PLC projects before deserialization
• Monitor for anomalous process execution: Alert on unexpected child processes spawned by TIA Portal or STEP 7 Safety components
• Reference Microsoft CA2300 guidance for additional .NET deserialization hardening recommendations

Evidence notes

Vulnerability disclosed via CISA ICS advisory ICSA-24-193-12 with Siemens security advisory SSA-313039. CVSS 3.1 vector confirms local attack vector with high complexity and privilege requirements. Microsoft CA2300 reference establishes this as a known .NET deserialization pattern.

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.