Full Report
Desigo CC and Cerberus DMS are based on SIMATIC WinCC OA and implement client-side only authentication for specific parts of their client-server communication. In this configuration, attackers could impersonate other users or exploit the client-server protocol without being authenticated, as documented for SIMATIC WinCC OA in SSA-111512 [1]. Siemens recommends specific mitigations, documented in [2], for products where fixes are not, or not yet available. Additional details regarding these mitigations can be found in the chapter Additional Information. [1] https://cert-portal.siemens.com/productcert/html/ssa-111512.html [2] https://support.industry.siemens.com/cs/ww/en/view/109813389/
Analysis Summary
# Vulnerability: Client-Side Authentication Bypass in Desigo CC and Cerberus DMS
## CVE Details
* **CVE ID:** CVE-2022-33139 (Inherited from SIMATIC WinCC OA)
* **CVSS Score:** 8.8 (High)
* **CWE:** CWE-603: Use of Client-Side Authentication
## Affected Systems
* **Products:**
* Siemens Desigo CC
* Siemens Cerberus DMS
* **Versions:** All versions based on SIMATIC WinCC OA (specifically those prior to the implementation of the Kerberos/SSC authentication updates).
* **Configurations:** Systems utilizing the client-server protocol where server-side verification of authentication is not enforced for specific communication components.
## Vulnerability Description
The affected products are built upon the SIMATIC WinCC OA framework. The vulnerability arises because the client-server communication protocol implements **client-side only authentication** for specific functions. In this architecture, the server relies on the client to perform the identity verification. An attacker can bypass this by utilizing a custom client or modifying the communication stream to claim an identity without providing valid credentials. This allows for unauthorized impersonation of users and the ability to execute commands within the client-server protocol.
## Exploitation
* **Status:** PoC concepts are documented for the underlying WinCC OA protocol; however, active "in the wild" exploitation specifically targeting Desigo CC/Cerberus DMS via this vector is not explicitly reported in the provided text.
* **Complexity:** Medium (Requires knowledge of the proprietary client-server protocol).
* **Attack Vector:** Network (The flaw is exploitable over the network via the protocol's communication port).
## Impact
* **Confidentiality:** High (Access to sensitive building management or fire safety data).
* **Integrity:** High (Ability to modify system configurations or trigger unauthorized actions).
* **Availability:** High (Potential to disrupt services or crash the communication manager).
## Remediation
### Patches
Siemens is releasing updates for various product lines. Users are advised to check the Siemens ProductCERT portal for the specific version-fix mapping for Desigo CC and Cerberus DMS.
### Workarounds
* **Enable Stronger Authentication:** For products where fixes are not yet available, Siemens recommends implementing the "Secure Communication" (SSC) features and Kerberos-based authentication as detailed in the referenced documentation.
* **Network Segmentation:** Isolate the building automation network (BACnet/Management level) from the general corporate network.
* **VPN/Encrypted Tunnels:** Ensure all remote access to the client-server communication is conducted via encrypted VPN tunnels.
## Detection
* **Indicators of Compromise:** Unusual login patterns or administrative actions originating from unexpected IP addresses; unauthorized attempts to connect to the WinCC OA management ports (e.g., TCP/5678 or configured project ports).
* **Detection methods and tools:** Monitor network traffic for unauthenticated protocol handshake attempts. Use Siemens-specific diagnostic tools to audit active sessions and verify if "Secure Communication" is active.
## References
* Siemens SSA-111512: hxxps[://]cert-portal[.]siemens[.]com/productcert/html/ssa-111512[.]html
* Siemens Support Mitigations (109813389): hxxps[://]support[.]industry[.]siemens[.]com/cs/ww/en/view/109813389/