A vulnerability has been identified in SINUMERIK 828D V4.7 (All versions < V4.7 SP6 HF1), SINUMERIK 840D sl V4.7 (All versions < V4.7 SP6 HF5), SINUMERIK 840D sl V4.8 (All versions < V4.8 SP3). The integrated VNC server on port 5900/tcp of the affected products could allow a remote attacker to cause a Denial-of-Service condition of the VNC server. Please note that this vulnerability is only exploitable if port 5900/tcp is manually opened in the firewall configuration of network port X130. The security vulnerability could be exploited by an attacker with network access to the affected devices and port. Successful exploitation requires no privileges and no user interaction. The vulnerability could allow an attacker to compromise availability of the VNC server. At the time of advisory publication no public exploitation of this security vulnerability was known.