The latest update for Desigo PXC devices fixes a vulnerability that could allow unauthenticated remote users to cause a denial of service condition on the PX Web interface (HTTP, port tcp/80) of a device. Devices where PX Web is not enabled are not affected by this vulnerability.
As a general security measure Siemens strongly recommends to protect network access to affected products with appropriate mechanisms. It is advised to follow recommended security practices in order to run the devices in a protected IT environment.
The Desigo PX automation stations and operator units control and monitor building automation systems. They allow for alarm signaling, time-based programs and trend logging.
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/.
The device contains a vulnerability that could allow an attacker to cause a denial of service condition on the device's web server by sending a specially crafted HTTP message to the web server port (tcp/80).
The security vulnerability could be exploited by an attacker with network access to an affected device. Successful exploitation requires no system privileges and no user interaction. An attacker could use the vulnerability to compromise the availability of the device's web service. While the device itself stays operational, the web server responds with HTTP status code 404 (Not found) to any further request. A reboot is required to recover the web interface.
At the time of advisory publication no public exploitation of this security vulnerability was known.