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Siemens S7-1200 and S7-200 SMART CPUs (Update B)

Monitor6.8ICS-CERT ICSA-19-318-02Nov 12, 2019
Attack VectorPhysical
Auth RequiredNone
ComplexityLow
User InteractionNone needed
Summary

Siemens S7-1200 and S7-200 SMART CPUs contain a firmware defect (CWE-749) that allows an attacker with physical access to the CPU to bypass security protections and execute arbitrary code. The vulnerability affects all current versions of the S7-1200 pre-v4.x family and all S7-200 SMART models up to specific version thresholds. S7-1200 v4.x versions prior to v4.4.1 FS11 are vulnerable; older v4.x and pre-v4.x models cannot be patched. S7-200 SMART models (ST, SR, CR series) are vulnerable up to v2.5.0 (ST/SR) and v2.2.2–v2.3.0 (CR models). An attacker exploiting this could modify control logic, alter setpoints, or halt production without valid credentials.

What this means
What could happen
An attacker with physical access to a Siemens S7-1200 or S7-200 SMART CPU can bypass security mechanisms and execute arbitrary code on the PLC, potentially altering control logic, process setpoints, or shutting down operations without authorization.
Who's at risk
Water and power utilities, chemical processing plants, and any industrial facility using Siemens S7-1200 or S7-200 SMART programmable logic controllers for critical automation. This affects both the newer S7-1200 line and the older S7-200 SMART models, including SIPLUS variants rated for harsh environments. Equipment includes all CPU models in these product families currently deployed.
How it could be exploited
An attacker with physical access to the CPU (via direct connection to debug/programming port or physical tampering) can exploit a firmware defect to bypass authentication and load malicious control code that alters plant operations.
Prerequisites
  • Physical access to the S7-1200 or S7-200 SMART CPU
  • Ability to connect to debug or programming interface
  • No valid PLC engineering credentials required
No patch available for S7-1200 pre-v4.x modelsPhysical access required but plausible in industrial plantsAffects safety-critical control systemsNo authentication required once physical access is gainedVulnerability cannot be mitigated on legacy hardware unable to accept firmware updates
Exploitability
Low exploit probability (EPSS 0.1%)
Affected products (16)
14 with fix2 pending
ProductAffected VersionsFix Status
SIMATIC S7-200 SMART CPU ST20 (6ES7 288-1ST20-0AA0): All≤ V2.5.0 and Function State FS 9v2.5.1 and latest boot loader
SIMATIC S7-200 SMART CPU SR20 (6ES7 288-1SR20-0AA0): All≤ V2.5.0 and Function State FS 11v2.5.1 and latest boot loader
SIMATIC S7-200 SMART CPU SR30 (6ES7 288-1SR30-0AA0): All≤ V2.5.0 and Function State FS 10v2.5.1 and latest boot loader
SIMATIC S7-200 SMART CPU CR20s (6ES7 288-1CR20-0AA1): All≤ V2.3.0 and Function State FSlatest boot loader (firmware remains v2.3.0)
SIMATIC S7-200 SMART CPU CR60s (6ES7 288-1CR60-0AA1): All≤ V2.3.0 and Function State FSlatest boot loader (firmware remains v2.3.0)
Remediation & Mitigation
0/7
Do now
0/1
HARDENINGRestrict physical access to the CPU and ensure debug/programming ports are physically protected or locked
Schedule — requires maintenance window
0/4

Patching may require device reboot — plan for process interruption

HOTFIXUpdate SIMATIC S7-1200 CPU family v4.x to v4.4.1 (FS >= 11)
HOTFIXUpdate SIMATIC S7-200 SMART CPUs (ST/SR series) to v2.5.1 or later with latest boot loader
HOTFIXUpdate SIMATIC S7-200 SMART CPUs (CR series) to v2.2.3 or later (CR40/CR60) or v2.3.0 with latest boot loader (CR20s/CR30s/CR40s/CR60s)
HARDENINGLimit network access to the CPU to authorized engineering workstations only
Long-term hardening
0/2
HARDENINGFor S7-1200 CPU family prior to v4.x that cannot be updated: implement physical access controls to CPU hardware
HARDENINGIsolate control system networks from the business network using firewalls
View full CISA ICS-CERT advisory
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