Siemens SIMATIC

Monitor5.9ICS-CERT ICSA-23-222-09Aug 8, 2023

Attack VectorNetwork

Auth RequiredNone

ComplexityHigh

User InteractionNone needed

Summary

Multiple Siemens SIMATIC products are affected by a timing-based side-channel vulnerability in OpenSSL RSA Decryption (CVE-2023-4304). An attacker with network access can observe the timing of RSA decryption operations and statistically extract the private key over multiple observations, compromising the confidentiality of encrypted communications between controllers, engineering workstations, and remote gateways. The vulnerability exists in the OpenSSL cryptographic library used by Siemens firmware for RSA key operations. Affected products include S7-1200 and S7-1500 PLC families, ET 200 distributed I/O modules, SIMATIC Cloud Connect 7 gateways, Process Historian servers, and related software tools. Siemens has released firmware updates for most products; however, several legacy and specialized models (certain S7-1500 variants, SIMATIC Logon V1.6, and Process Historian 2019/2020) will not receive fixes due to end-of-life status.

What this means

What could happen

An attacker who can intercept encrypted RSA communications with a Siemens controller could use timing analysis to extract the private key over time, compromising confidentiality of encrypted process data and control commands. This affects systems using OpenSSL RSA decryption for device-to-device or device-to-workstation encrypted communications.

Who's at risk

This affects Siemens SIMATIC programmable logic controllers (PLCs), industrial PCs, and gateway devices widely used in manufacturing and transportation. Specifically impacted are: S7-1200 and S7-1500 PLC families, ET 200S/ET 200pro distributed I/O modules, Cloud Connect 7 industrial IoT gateways, Process Historian OPC UA servers, PDM (Process Device Management) software, and SIMATIC Logon user management systems. These are the controllers and systems that manage production lines, conveyor systems, motor drives, process loops, and safety-critical functions in plants. Organizations running Siemens automation equipment should check their firmware versions against the affected list.

How it could be exploited

An attacker on the network observes the time it takes for RSA decryption operations on the target controller. By capturing many encrypted messages and measuring decryption timing differences, the attacker can statistically extract bits of the private key without needing to break into the device directly. This requires network access to measure timing but no authentication.

Prerequisites

Network access to monitor encrypted traffic to/from the affected Siemens controller
Ability to capture multiple RSA-encrypted messages and measure precise decryption timing (millisecond-level precision)
No authentication required to observe network timing
Controller must be using OpenSSL for RSA decryption (built into the SIMATIC firmware)

Remotely exploitable over networkNo authentication required to capture timing informationTiming-based side-channel attack (low complexity for attacker with network sniffer)Affects confidentiality of encrypted communicationsMultiple product families with no fix planned (end-of-life products)High number of affected device models and versions

Exploitability

Low exploit probability (EPSS 0.3%)

Affected products (150)

127 with fix23 pending

ProductAffected VersionsFix Status

SIMATIC S7-1500 CPU 1511TF-1 PN<V3.0.33.0.3

SIMATIC S7-1500 CPU 1512C-1 PN<V2.9.72.9.7

SIMATIC S7-1500 CPU 1512SP F-1 PNAll versionsNo fix yet

SIMATIC S7-1500 CPU 1512SP F-1 PN<V2.9.72.9.7

SIMATIC S7-1500 CPU 1512SP F-1 PN<V3.0.33.0.3

Remediation & Mitigation

0/12

Schedule — requires maintenance window

0/10

Patching may require device reboot — plan for process interruption

Long-term hardening

0/2

SIMATIC Logon V1.6

HARDENINGFor products with no fix available (SIMATIC Logon V1.6, SIMATIC PDM V9.1, SIMATIC Process Historian 2019/2020 OPC UA Server, and certain S7-1500 CPU models marked 'All versions'): Implement network segmentation to restrict access to these controllers to authorized engineering and operation networks only

All products

HARDENINGFor products with no fix available: Disable or limit RSA-encrypted communications where possible; use firewall rules to restrict which hosts can communicate with affected controllers

CVEs (1)

CVE-2022-4304

View full CISA ICS-CERT advisory

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