-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

# SSA-914382: Denial-of-Service Vulnerability in SIMATIC S7-400 CPU Family

Publication Date:        2018-05-15
Last Update:             2020-02-10
Current Version:         1.2
CVSS v3.1 Base Score:    7.5

SUMMARY
=======

SIMATIC S7-400 CPUs are affected by a security vulnerability which could
lead to a Denial-of-Service condition of the PLC if specially crafted
packets are received and processed.

The affected SIMATIC S7-400 CPU hardware versions are in the product
cancellation phase or already phased-out. Siemens recommends customers
either upgrading to a new version or implementing specific
countermeasures.


AFFECTED PRODUCTS AND SOLUTION
==============================


* SIMATIC S7-400 CPU hardware version 4.0 and below (incl. SIPLUS
variants) 
  - Affected versions:
       All versions
  - Remediation:
       See recommendations from section Workarounds and Mitigations or upgrade
       to hardware version 5.0 or newer
  - Download:
       https://support.industry.siemens.com/cs/ww/en/view/109483507

* SIMATIC S7-400 CPU hardware version 5.0 (incl. SIPLUS variants) 
  - Affected versions:
       All firmware versions < V5.2
  - Remediation:
       Update to firmware version 5.2 or newer
  - Download:
       https://support.industry.siemens.com/cs/ww/en/view/109474827

* SIMATIC S7-400 H CPU hardware version 4.5 and below (incl. SIPLUS
variants) 
  - Affected versions:
       All versions
  - Remediation:
       See recommendations from section Workarounds and Mitigations or upgrade
       to hardware version 6.0 or newer
  - Download:
       https://support.industry.siemens.com/cs/ww/en/view/75407031


WORKAROUNDS AND MITIGATIONS
===========================

Siemens has identified the following specific workarounds and mitigations that
customers can apply to reduce the risk:

* Apply cell protection concept:
https://www.siemens.com/cert/operational-guidelines-industrial-security.
  
* Use VPN for protecting network communication between cells.
  
* Apply Defense-in-Depth:
https://www.siemens.com/cert/operational-guidelines-industrial-security.
  


GENERAL SECURITY RECOMMENDATIONS
================================

As a general security measure, Siemens strongly recommends to protect
network access to devices with appropriate mechanisms. In order to
operate the devices in a protected IT environment, Siemens recommends to
configure the environment according to Siemens' operational guidelines
for Industrial Security (Download:
https://www.siemens.com/cert/operational-guidelines-industrial-security),
and to follow the recommendations in the product manuals.

Additional information on Industrial Security by Siemens can be found
at: https://www.siemens.com/industrialsecurity

PRODUCT DESCRIPTION
===================

Products in the SIMATIC S7-400 CPU family have been designed for process
control in industrial environments. They are used worldwide, e.g. in the
automotive industry, mechanical equipment manufacture, warehousing
systems, building engineering, steel industry, power generation and
distribution, pharmaceuticals, food and beverages industry, or chemical
industry.

SIPLUS extreme products are designed for reliable operation under
extreme conditions and are based on SIMATIC, LOGO!, SITOP, SINAMICS,
SIMOTION, SCALANCE or other devices. SIPLUS devices use the same
firmware as the product they are based on.

VULNERABILITY CLASSIFICATION
============================

The vulnerability classification has been performed by using the CVSS scoring
system in version 3.1 (CVSS v3.1) (https://www.first.org/cvss/). The CVSS 
environmental score is specific to the customer's environment and will impact
the overall CVSS score. The environmental score should therefore be 
individually defined by the customer to accomplish final scoring.

An additional classification has been performed using the CWE classification, a
community-developed list of common software security weaknesses. This serves as
a common language and as a baseline for weakness identification, mitigation,
and prevention efforts. A detailed list of CWE classes can be found at:
https://cwe.mitre.org/.



* Vulnerability CVE-2018-4850

  The affected CPUs improperly validate S7 communication packets which
  could cause a Denial-of-Service condition of the CPU. The CPU will
  remain in DEFECT mode until manual restart.
  
  Successful exploitation requires an attacker to be able to send a
  specially crafted S7 communication packet to a communication interface
  of the CPU. This includes Ethernet, PROFIBUS, and Multi Point Interfaces
  (MPI). No user interaction or privileges are required to exploit the
  security vulnerability. The vulnerability could allow causing a
  Denial-of-Service condition of the core functionality of the CPU,
  compromising the availability of the system.
  
  At the time of advisory publication no public exploitation of this
  security vulnerability was known. Siemens confirms the security
  vulnerability and provides mitigations to resolve the security issue.

  CVSS v3.1 Base Score: 7.5
  CVSS Vector:          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C
  CWE:                  CWE-20: Improper Input Validation


ACKNOWLEDGMENTS
===============

Siemens thanks the following parties for their efforts:

   * Artem Zinenko from Kaspersky for pointing out that SIPLUS should also be mentioned



ADDITIONAL INFORMATION
======================

For further inquiries on security vulnerabilities in Siemens products and 
solutions, please contact the Siemens ProductCERT:

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


HISTORY DATA
============

V1.0 (2018-05-15): Publication Date
V1.1 (2018-09-11): Added hint to Workarounds section
V1.2 (2020-02-10): SIPLUS devices now explicitly mentioned in the list of affected products

TERMS OF USE
============

Siemens Security Advisories are subject to the terms and conditions contained
in Siemens' underlying license terms or other applicable agreements previously
agreed to with Siemens (hereinafter "License Terms"). To the extent applicable
to information, software or documentation made available in or through a
Siemens Security Advisory, the Terms of Use of Siemens' Global Website
(https://www.siemens.com/terms_of_use, hereinafter "Terms of Use"), in
particular Sections 8-10 of the Terms of Use, shall apply additionally. In case
of conflicts, the License Terms shall prevail over the Terms of Use.
-----BEGIN PGP SIGNATURE-----

iQIcBAEBCgAGBQJeQJ0AAAoJENP0geoRSq/kut8QAIRBJNj5JqM+poZ8jYiRyWzE
9aTulNdyT5bx308kodpFRZ1ai5JmHo40ptVi0NPqVr928Z/tUL7S7fL2XSzvjrDu
FyRBliAV9NakzLhpgEb6tb7PoNmKStakNxC2Eu4gAUt+rwbqC3X8ecE6z3gXykkP
2L+o/3YAr4dKv0RVZ2fPztf1SFZRRtCQBUh3eOZC3MJkLQ2RpwwJ5WUSk+g806ca
o5ratwqeNXmwUYrmF7ZySn6h3vvAeu05LEIpI5eM0ngz1OTj65540mh9LJBLwtcO
Bg+5WBVWhtdIhCBdQgdMMGgtDpE9liWzFcr/NPEUGy+97NxGOegs8wCIeOy81Kuj
KUZ9MOKSwiaOIbJ0kSsfUk4yOdeIlRLZVAgZsT+qmlOG1zKMUEbEPBpwsdOWrEy5
jyzC4B5IqCfhmKdFarzok7jHBM2uHqHp1kMQez+pH+WTdC+ZTP2FslG6fEIcVE6m
EkzCQa5IxF/nBAPSDwXW/pVFTQ1o0b5uJm4HQFjPxhVd7fINjSHHfRLn8py0+tpM
UEDb/tQaozv4M3zWP4aVr+sl4IRwkc7P8rDrewbv7+KM4qjlgV+ywm6Vgx0roxuH
MF3NZxv0wsYPZKbOdnzs+V0Dp3JiTTQ/8uODWiteHciixOcJM177tRNxLyE3I/BS
1zeOm+SBMsRZ3/Ef/xzN
=AqZm
-----END PGP SIGNATURE-----