Full Report
Security experts have examined the SIMATIC S7-1200 Programmable Logic Controller (PLC). This research has revealed some weaknesses in the SIMATIC S71200 CPU communication and authentication functions. Once the automation network is compromised it is possible to demonstrate the following weaknesses using a remote exploit: - Trigger CPU functions by record and playback of legitimate network communication - Place CPU in stop/defect state by causing a communications error A remote exploit is a type of attack that can be launched from one computer against another computer across a network. For example, a PC with access to the automation network could be used to launch a remote exploit against a PLC. The weaknesses are closed with a firmware update V 2.0.3. For the second weakness (communications error), a temporary work-around is also available: if the Web server on the S7-1200 is disabled, the weakness cannot be exploited.
Analysis Summary
# Vulnerability: Siemens SIMATIC S7-1200 Communication and Authentication Flaws
## CVE Details
*Note: The provided text describes historical vulnerabilities related to the S7-1200 series (likely associated with CVE-2011-3323 and CVE-2011-3326 based on the firmware version provided).*
- **CVE ID:** CVE-2011-3323, CVE-2011-3326 (Context dependent)
- **CVSS Score:** ~7.5 - 7.8 (High) - *Estimated based on industrial impact*
- **CWE:** CWE-294 (Authentication Bypass by Capture-replay), CWE-20 (Improper Input Validation)
## Affected Systems
- **Products:** Siemens SIMATIC S7-1200 PLC CPUs
- **Versions:** All firmware versions prior to V2.0.3
- **Configurations:** Systems where the Web Server is enabled (specifically for the DoS vulnerability) and systems reachable via an untrusted automation network.
## Vulnerability Description
Two distinct weaknesses were identified in the S7-1200 CPU communication stack:
1. **Replay Attack Vulnerability:** A lack of robust authentication or session freshness in the communication protocol allows an attacker to capture legitimate network traffic and "replay" it later to trigger CPU functions without knowing the original credentials.
2. **Resource Exhaustion / Communications Error:** A flaw in the handling of network packets (specifically related to the Web Server component) allows a remote attacker to cause a communications error, forcing the CPU into a "Stop" or "Defect" state.
## Exploitation
- **Status:** PoC demonstrated by security researchers.
- **Complexity:** Medium (Requires access to the automation network and ability to capture/inject traffic).
- **Attack Vector:** Network (Remote exploit).
## Impact
- **Confidentiality:** None to Low.
- **Integrity:** High (Unauthorized triggering of CPU functions/commands).
- **Availability:** High (Ability to force the PLC into a stopped or defective state, halting industrial processes).
## Remediation
### Patches
- **Firmware Update:** Upgrade SIMATIC S7-1200 CPU firmware to **Version 2.0.3** or higher.
### Workarounds
- **Disable Web Server:** For the communications error/DoS weakness, disabling the integrated Web Server on the S7-1200 mitigates the specific attack vector.
- **Network Segmentation:** Ensure the automation network is isolated from the corporate/public internet to prevent remote access by unauthorized actors.
## Detection
- **Indicators of Compromise:**
- Unexpected CPU transitions to "STOP" or "DEFECT" mode.
- Unexplained execution of commands or logic changes not initiated by authorized engineering stations.
- **Detection Methods:**
- Network traffic monitoring for repeated, identical command sequences (Replay detection).
- Monitoring for malformed HTTP traffic targeting the PLC's IP address.
## References
- **Vendor Advisory:** Siemens ProductCERT
- **Relevant Links:**
- hxxps[://]www[.]siemens[.]com/cert
- hxxps[://]support[.]industry[.]siemens[.]com/cs/document/51745116/