A vulnerability has been identified in Desigo PX automation controllers PXC00-E.D, PXC50-E.D, PXC100-E.D, PXC200-E.D with Desigo PX Web modules PXA40-W0, PXA40-W1, PXA40-W2 (All firmware versions < V6.00.320), Desigo PX automation controllers PXC00-U, PXC64-U, PXC128-U with Desigo PX Web modules PXA30-W0, PXA30-W1, PXA30-W2 (All firmware versions < V6.00.320), Desigo PX automation controllers PXC22.1-E.D, PXC36-E.D, PXC36.1-E.D with activated web server (All firmware versions < V6.00.320). 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.