PT-2013-84: 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: