PT-2013-84: Insuffient Entropy in Siemens SIMATIC S7-1500 CPU PLC

(PT-2013-84) Positive Technologies Security Advisory
Insuffient Entropy in Siemens SIMATIC S7-1500 CPU PLC

Vulnerable platform

Siemens SIMATIC S7-1500 CPU PLC
Version: 1.1.x and earlier


Severity level

Severity level: High
Impact: Session Hijaking, Information Disclosure, Denial of Service
Access Vector: Remote

CVSS v2:
Base Score: 8.3
Vector: (AV:N/AC:M/Au:N/C:P/I:P/A:C)

CVE: CVE-2014-2251

Platform description

Siemens SIMATIC S7-1500 - controllers featuring high efficiency in data processing, integrated technological functions of Motion Control, PID control and the use of high-speed counters..

Vulnerability description

The specialists of the Positive Research center have detected an Insuffient Entropy vulnerability in Siemens SIMATIC S7-1500 CPU PLC.

Due to low entropy in its random number generator, the authentication of the integrated web server (port 80/tcp and port 443/tcp) of S7-1500 PLCs might allow attackers to hijack web sessions over the network without authentication.

How to fix

Update your firmware up to the latest version

Advisory status

05.08.2013 - Vendor gets vulnerability details
12.03.2014 - Vendor releases fixed version and details
25.03.2014 - Public disclosure


The vulnerability was detected by Alexey Osipov and Alexander Timorin, Positive Research Center (Positive Technologies Company)


Reports on the vulnerabilities previously discovered by Positive Research:

About Positive Technologies

Positive Technologies is a leading provider of vulnerability assessment, compliance management and threat analysis solutions to more than 1,000 global enterprise clients. Our solutions work seamlessly across your entire business: securing applications in development; assessing your network and application vulnerabilities; assuring compliance with regulatory requirements; and blocking real-time attacks. Our commitment to clients and research has earned Positive Technologies a reputation as one of the foremost authorities on SCADA, Banking, Telecom, Web Application and ERP security, and distinction as the #1 fastest growing Security and Vulnerability Management firm in 2012, as shown in an IDC report*. To learn more about Positive Technologies please visit

*Source: IDC Worldwide Security and Vulnerability Management 2013-2017 Forecast and 2012 Vendor Shares, doc #242465, August 2013. Based on year-over-year revenue growth in 2012 for vendors with revenues of $20M+