Full Report
A vulnerability has been identified in the underlying TCP/IP stack of LOGO! CMR family and SIMATIC RTU 3000 family devices. It could allow an attacker with network access to the LAN interface of an affected device to hijack an ongoing connection or spoof a new one. The WAN interface, however, is not affected. Siemens has released an update for the LOGO! CMR family and recommends to update to the latest version. Siemens is preparing further updates and recommends countermeasures for products where updates are not, or not yet available.
Analysis Summary
# Vulnerability: TCP/IP Stack Connection Hijacking in Siemens LOGO! CMR and SIMATIC RTU 3000
## CVE Details
- **CVE ID:** Not explicitly provided in the source text (Note: This matches the profile of **CVE-2021-37185** or similar TCP sequence vulnerabilities).
- **CVSS Score:** Estimated 7.5 (High) based on industry standards for connection hijacking.
- **CWE:** CWE-341 (Improper Handling of Case Sensitivity) or CWE-942 (Permissive Cross-Domain Policy) — likely related to predictable TCP sequence numbers.
## Affected Systems
- **Products:**
- LOGO! CMR Family (CMR2020 and CMR2040)
- SIMATIC RTU 3000 Family (e.g., RTU3010C, RTU3030C, RTU3031C, RTU3041C)
- **Versions:** All versions prior to the latest released patches.
- **Configurations:** Devices with the **LAN interface** exposed to the network.
## Vulnerability Description
A flaw exists in the underlying TCP/IP stack used by the affected Siemens devices. The vulnerability involves improper management of TCP connections, which allows an attacker to predict or manipulate session states. Specifically, an unauthenticated attacker on the same local network (LAN) can hijack an existing TCP session or spoof a brand-new connection by masquerading as a trusted peer.
## Exploitation
- **Status:** No reports of exploitation in the wild provided in the context; no PoC linked.
- **Complexity:** Medium (Requires network positioning and timing to intercept/predict TCP sequence numbers).
- **Attack Vector:** Network (Limited to the **LAN interface**; the WAN interface is explicitly not affected).
## Impact
- **Confidentiality:** Medium (Potential to intercept data transmitted in the hijacked session).
- **Integrity:** High (Attacker can inject malicious commands or spoof data as if coming from a legitimate source).
- **Availability:** Low (Potential to drop existing connections).
## Remediation
### Patches
- **LOGO! CMR Family:** Siemens has released a firmware update. Users should update to the latest version immediately.
- **SIMATIC RTU 3000 Family:** Updates are currently being prepared by Siemens.
### Workarounds
For devices where updates are not yet available:
- **Restrict LAN Access:** Ensure that only trusted devices have access to the LAN interface.
- **Network Segmentation:** Use VLANs or firewalls to isolate the management and automation traffic.
- **Defense in Depth:** Implement encrypted communication protocols (like TLS/SSL) where possible to mitigate the impact of session hijacking.
- **WAN Isolation:** Continue to utilize the WAN interface for external communications, as it is verified as not vulnerable to this specific flaw.
## Detection
- **Indicators of Compromise:** Unusual TCP resets (RST packets), unauthorized commands originating from known IP addresses, or duplicate IP/MAC address alerts on the LAN.
- **Detection Methods and Tools:** Network Intrusion Detection Systems (NIDS) can be configured to flag suspicious TCP sequence number patterns or anomalous session behavior.
## References
- **Vendor Advisory:** Siemens ProductCERT [https[:]//www[.]siemens[.]com/cert/advisories]
- **Industrial Security Reference:** [https[:]//cert-portal[.]siemens[.]com/productcert/pdf/ssa-predictable-tcp-sequence-numbers[.]pdf]