ICS Alert (ICS-ALERT-11-332-02A)

Siemens SIMATIC WinCC Flexible (Update A)

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This Alert Update is a follow-up to the original ICS-CERT Alert titled “ICS-ALERT-11-332-02—Siemens SIMATIC WinCC Flexible Vulnerabilities” that was published November 28, 2011 on the ICS-CERT web page.

ICS-CERT is aware of a public report of multiple vulnerabilities with proof-of-concept (PoC) exploit code affecting Siemens SIMATIC WinCC Flexible Runtime, a human-machine interface product. According to this report, the vulnerabilities are exploitable remotely via Port 2308/TCP. This report was released by Luigi Auriemma without coordination with ICS-CERT, the vendor, or other coordination entity that ICS-CERT is aware of.

ICS-CERT has coordinated the report with Siemens, who is working to confirm the report and identify mitigations. ICS-CERT is issuing this alert to provide early notice of the report and identify baseline mitigations for reducing risks to these and other cybersecurity attacks.

--------- Begin Update A Part 1 of 1 --------

The reported vulnerabilities affect WinCC Flexible Runtime Loader, a component of Siemens SIMATIC WinCC Flexible 2008. When the Runtime Loader is running in Transfer mode, it might be possible to remotely exploit the vulnerabilities via Port 2308/TCP.

The report includes vulnerability details and PoC exploit code for three vulnerabilities. Siemens has analyzed the vulnerability report and offered additional vulnerability characterization information.

The report includes details and PoC exploit code for the following vulnerabilities:

Vulnerability TypeExploitabilityImpact
Stack OverflowRemotePossible Remote Code Execution
Directory TraversalRemoteFile System Access
Memory Read AccessRemoteRuntime Transfer Denial of Service

--------- End Update A Part 1 of 1 ----------

ICS-CERT and Siemens are currently evaluating the reported stack overflow vulnerability, which may be the same as a previously reported vulnerability.

Please report any issues affecting control systems in critical infrastructure environments to ICS-CERT.


ICS-CERT released a follow-up advisory ICSA-12-030-01A - Siemens SIMATIC WinCC Vulnerabilities” to the ICS-CERT web page on April 17, 2012.


ICS-CERT is currently coordinating with the vendor to identify mitigations.

ICS-CERT recommends that users take defensive measures to minimize the risk of exploitation of these vulnerabilities. Specifically, users should:

  • Configure firewall rules appropriately for traffic on Port 2308/TCP.
  • Minimize network exposure for all control system devices. Control system devices should not directly face the Internet.a
  • Locate control system networks and devices behind firewalls, and isolate them from the business network.
  • If remote access is required, employ secure methods such as Virtual Private Networks (VPNs), recognizing that VPN is only as secure as the connected devices.

ICS-CERT reminds organizations to perform proper impact analysis and risk assessment prior to taking defensive measures.
The Control Systems Security Program (CSSP) also provides a recommended practices section for control systems on the US-CERT website. Several recommended practices are available for reading or download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies.

Organizations that observe any suspected malicious activity should follow their established internal procedures and report their findings to ICS-CERT for tracking and correlation against other incidents.

  • aICS-CERT ALERT, http://ics-cert.us-cert.gov/alerts/ICS-ALERT-10-301-01, website last accessed November 28, 2011.

Contact Information

For any questions related to this report, please contact the CISA at:

Email: CISAservicedesk@cisa.dhs.gov
Toll Free: 1-888-282-0870

For industrial control systems cybersecurity information:  https://us-cert.cisa.gov/ics 
or incident reporting:  https://us-cert.cisa.gov/report

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