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Insecure Storage of HTTPS CA Certificate in SIMATIC S7-1200 CPU V2

Monitor7.4SSA-240718Sep 13, 2012
Attack VectorNetwork
Auth RequiredNone
ComplexityHigh
User InteractionNone needed
Summary

SIMATIC S7-1200 CPU V2 devices store an insufficiently protected private key used for the HTTPS Certificate Authority. An attacker with possession of this key could create a forged web server certificate to spoof the device's web interface. This affects all versions of the S7-1200 CPU V2 family, including SIPLUS variants. Siemens has not released a firmware fix and recommends network protection measures and adherence to operational security guidelines.

What this means
What could happen
An attacker who obtains the hardcoded CA certificate private key could forge HTTPS certificates for the device's web interface, allowing them to impersonate the device and intercept or manipulate communications without detection.
Who's at risk
Water and electric utilities using SIMATIC S7-1200 CPU V2 controllers for process automation, pump control, tank level monitoring, or valve actuation should implement network controls. This affects any organization relying on the device's web interface for remote monitoring or configuration.
How it could be exploited
An attacker would need to extract the private key from the S7-1200 CPU V2 device (via direct access to the device memory, firmware analysis, or compromise of the device). With this key, they can create a forged certificate that the device's web interface will trust, positioning themselves as a man-in-the-middle between operators and the device's web server to intercept commands or display false process information.
Prerequisites
  • Direct or indirect access to extract the CA certificate private key from the device (requires device compromise or physical/firmware access)
  • Ability to intercept HTTPS traffic between operators and the device's web interface
  • Knowledge of the device's hostname or IP address to craft a matching forged certificate
remotely exploitablelow complexityno patch availableaffects monitoring and configuration interface
Exploitability
Low exploit probability (EPSS 0.4%)
Affected products (1)
ProductAffected VersionsFix Status
SIMATIC S7-1200 CPU V2 family (incl. SIPLUS variants)All versionsNo fix (EOL)
Remediation & Mitigation
0/4
Do now
0/1
WORKAROUNDRestrict network access to the S7-1200 CPU V2 web interface using firewall rules; only allow engineering workstations and authorized HMI systems to connect to HTTP/HTTPS ports (80/443)
Schedule — requires maintenance window
0/2

Patching may require device reboot — plan for process interruption

HARDENINGMonitor and log all HTTPS connections to the device's web interface to detect suspicious certificate validation failures or unusual access patterns
HARDENINGImplement certificate pinning on engineering workstations and HMI systems that connect to the device, if supported by the client software
Mitigations - no patch available
0/1
SIMATIC S7-1200 CPU V2 family (incl. SIPLUS variants) has reached End of Life. The vendor will not release a patch. Apply the following compensating controls:
HARDENINGSegment the control network from corporate IT networks and untrusted networks using air-gapping or firewalls
View full Siemens ProductCERT advisory
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Insecure Storage of HTTPS CA Certificate in SIMATIC S7-1200 CPU V2 | CVSS 7.4 - OTPulse