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             AUSCERT External Security Bulletin Redistribution

                               ESB-2019.2574
         Advisory (icsa-19-192-02) Siemens SIMATIC WinCC and PCS7
                               12 July 2019

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           Siemens SIMATIC WinCC
                   Siemens SIMATIC PCS7
Publisher:         ICS-CERT
Operating System:  Windows
Impact/Access:     Execute Arbitrary Code/Commands -- Existing Account
                   Create Arbitrary Files          -- Existing Account
                   Denial of Service               -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2019-10935  

Original Bulletin: 
   https://www.us-cert.gov/ics/advisories/icsa-19-192-02

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ICS Advisory (ICSA-19-192-02)

Siemens SIMATIC WinCC and PCS7

Original release date: July 11, 2019

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1. EXECUTIVE SUMMARY

  o CVSS v3 7.2
  o ATTENTION: Exploitable remotely/low skill level to exploit
  o Vendor: Siemens
  o Equipment: SIMATIC WinCC and SIMATIC PCS7
  o Vulnerability: Unrestricted Upload of File with Dangerous Type

2. RISK EVALUATION

Successful exploitation of this vulnerability could cause a denial-of-service
condition on the affected service or device.

3. TECHNICAL DETAILS

3.1 AFFECTED PRODUCTS

The following Siemens industrial products are affected:

  o SIMATIC PCS 7 v8.0: all versions
  o SIMATIC PCS 7 v8.1: all versions
  o SIMATIC PCS 7 v8.2: all versions prior to v8.2 SP1 with WinCC v7.4 SP1 Upd
    11
  o SIMATIC PCS 7 v9.0: all versions prior to v9.0 SP2 with WinCC v7.4 SP1 Upd
    11
  o SIMATIC WinCC Professional (TIA Portal v13): all versions
  o SIMATIC WinCC Professional (TIA Portal v14): all versions
  o SIMATIC WinCC Professional (TIA Portal v15): all versions
  o SIMATIC WinCC Runtime Professional v13: all versions
  o SIMATIC WinCC Runtime Professional v14: all versions
  o SIMATIC WinCC Runtime Professional v15: all versions
  o SIMATIC WinCC v7.2 and earlier: all versions
  o SIMATIC WinCC v7.3: all versions
  o SIMATIC WinCC v7.4: all versions prior to v7.4 SP1 Upd 11
  o SIMATIC WinCC v7.5: all versions prior to v7.5 Upd 3

3.2 VULNERABILITY OVERVIEW

3.2.1 UNRESTRICTED UPLOAD OF FILE WITH DANGEROUS TYPE CWE-434

The SIMATIC WinCC DataMonitor web application of the affected products allows
an authenticated user with network access to the WinCC DataMonitor application
to upload arbitrary ASPX code.
Successful exploitation requires no user interaction and may impact the
confidentiality, integrity, and availability of the affected device. The
vulnerability is relevant only in situations where an attacker has access via
the web interface but not to the directory structure.

CVE-2019-10935 has been assigned to this vulnerability. A CVSS v3 base score of
7.2 has been calculated; the CVSS vector string is ( AV:N/AC:L/PR:H/UI:N/S:U/
C:H/I:H/A:H ).

3.3 BACKGROUND

  o CRITICAL INFRASTRUCTURE SECTORS: Chemical, Critical Manufacturing, Energy,
    Food and Agriculture, Water and Wastewater Systems
  o COUNTRIES/AREAS DEPLOYED: Worldwide
  o COMPANY HEADQUARTERS LOCATION: Germany

3.4 RESEARCHER

Xuchen Zhu from ZheJiang Guoli Security Technology and CNCERT/CC reported this
vulnerability to Siemens.

4. MITIGATIONS

Siemens currently has updates for the following products:

  o SIMATIC PCS 7 v8.2: Update WinCC to v7.4 SP1 Upd 11
  o SIMATIC PCS 7 v9.0: Update WinCC to v7.4 SP1 Upd 11
  o SIMATIC WinCC v7.4: Update WinCC to v7.4 SP1 Upd 11
  o SIMATIC WinCC v7.5: Update WinCC to v7.5 Upd 3

For the balance of the listed products, Siemens is preparing further updates
and recommends users apply the following specific workarounds and mitigations
to reduce risk until patches are available:

  o Apply defense in depth.

Siemens recommends users configure their environment according to Siemens'
operational guidelines for industrial security ( Download ) and follow the
recommendations in the product manuals.

Additional information on Industrial Security by Siemens can be found at:

https://www.siemens.com/industrialsecurity

For more information on the vulnerability and more detailed mitigation
instructions, please see Siemens security advisory SSA-121293 at the following
location:

http://www.siemens.com/cert/advisories

NCCIC recommends users take defensive measures to minimize the risk of
exploitation of this vulnerability. Specifically, users should:

  o Minimize network exposure for all control system devices and/or systems,
    and ensure that they are not accessible from the Internet .
  o Locate control system networks and remote devices behind firewalls, and
    isolate them from the business network.
  o When remote access is required, use secure methods, such as Virtual Private
    Networks (VPNs), recognizing that VPNs may have vulnerabilities and should
    be updated to the most current version available. Also recognize that VPN
    is only as secure as the connected devices.

NCCIC reminds organizations to perform proper impact analysis and risk
assessment prior to deploying defensive measures.

NCCIC also provides a section for control systems security recommended
practices on the ICS-CERT web page. Several recommended practices are available
for reading and download, including Improving Industrial Control Systems
Cybersecurity with Defense-in-Depth Strategies .

Additional mitigation guidance and recommended practices are publicly available
on the ICS-CERT website in the Technical Information Paper,
ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation
Strategies .

Organizations observing any suspected malicious activity should follow their
established internal procedures and report their findings to NCCIC for tracking
and correlation against other incidents.

No known public exploits specifically target this vulnerability.

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