Full Report
For the convenience of the customer, a Certificate Authority (CA) for HTTPS connections is installed on the Siemens SIMATIC S7-1200 PLC. The user has the option to trust this CA which if selected installs the certificate into the browser’s certificate store. Once the user completes this step, the browser will trust any other S7-1200 V2.x PLC on the network. A researcher has demonstrated the ability to obtain the private key of the S7-1200 CA ("SIMATIC CONTROLLER"). With this private key, an attacker is able to create his own certificate. Using this forged certificate, it is possible to spoof any SSL server certificate and conduct man-in-the-middle attacks on a user’s browser that is currently trusting this CA.
Analysis Summary
# Vulnerability: Siemens SIMATIC S7-1200 Hardcoded CA Private Key
## CVE Details
- **CVE ID:** CVE-2015-1601
- **CVSS Score:** 7.5 (High) - *Based on CVSS v2.0*
- **CWE:** CWE-321: Use of Hard-coded Cryptographic Key
## Affected Systems
- **Products:** Siemens SIMATIC S7-1200 PLC
- **Versions:** Firmware versions V2.x
- **Configurations:** Systems where the user has manually trusted the built-in "SIMATIC CONTROLLER" Certificate Authority (CA) and installed it into their browser’s root certificate store.
## Vulnerability Description
The Siemens SIMATIC S7-1200 PLC (V2.x) utilizes a built-in Certificate Authority (CA) to facilitate HTTPS connections for its web-based management interface. It was discovered that the private key for this "SIMATIC CONTROLLER" CA is identical across all devices in this product line.
If a user trusts this CA in their browser, the browser will inherently trust any certificate signed by that specific private key. Because the private key has been extracted, an attacker can use it to generate fraudulent SSL certificates that the victim's browser will treat as legitimate.
## Exploitation
- **Status:** PoC demonstrated by researchers.
- **Complexity:** Medium (Requires extracting the key from firmware or hardware once, then positioning for MITM).
- **Attack Vector:** Network / Adjacent (Man-in-the-Middle).
## Impact
- **Confidentiality:** High (Attacker can decrypt HTTPS traffic and steal credentials/data).
- **Integrity:** High (Attacker can inject malicious scripts or modify data in transit).
- **Availability:** Low (Primary impact is on data security, not PLC uptime).
## Remediation
### Patches
- **Update Firmware:** Users should upgrade to S7-1200 V3.0 or higher. Siemens introduced unique, device-specific certificates in later versions to replace the shared CA model.
### Workarounds
- **Remove Trusted CA:** Immediately remove the "SIMATIC CONTROLLER" CA from all web browser and operating system certificate stores.
- **Avoid HTTPS via PLC Web Server:** Use alternative management methods or ensure the PLC is behind a VPN/secure gateway that does not rely on the internal PLC CA for end-to-end encryption.
- **Isolate Management Traffic:** Ensure that the PLC management interface is only accessible via a dedicated, secure management VLAN.
## Detection
- **Indicators of Compromise:** Observation of SSL certificates for external websites (e.g., google.com, bank sites) that appear to be issued by "SIMATIC CONTROLLER" during an active session.
- **Detection Methods:**
- Network Security Monitoring (NSM) tools can be configured to flag any certificates signed by the known vulnerable SIMATIC CA key.
- Audit browser root stores for the presence of the "SIMATIC CONTROLLER" certificate.
## References
- **Siemens Security Advisory:** hxxps[://]www[.]siemens[.]com/cert/advisories
- **ICS-CERT Advisory:** hxxps[://]www[.]cisa[.]gov/news-events/ics-advisories/icsa-15-127-01
- **NVD Entry:** hxxps[://]nvd[.]nist[.]gov/vuln/detail/CVE-2015-1601