RealVNC VNC 5.0.6 on Mac OS X, Linux, and UNIX allows local users to gain privileges via a crafted argument to the (1) vncserver, (2) vncserver-x11, or (3) Xvnc helper.

RealVNC Viewer 6.21.406 allows remote VNC servers to cause a denial of service (application crash) via crafted RFB protocol data. NOTE: It is asserted that this issue requires social engineering a user into connecting to a fake VNC Server. The VNC Viewer application they are using will then hang, until terminated, but no memory leak occurs - the resources are freed once the hung process is terminated and the resource usage is constant during the hang. Only the process that is connected to the fake Server is affected. This is an application bug, not a security issue

RealVNC VNC Server 6.9.0 through 5.1.0 for Windows allows local privilege escalation because an installer repair operation executes %TEMP% files as SYSTEM.

RealVNC VNC Server before 6.11.0 and VNC Viewer before 6.22.826 on Windows allow local privilege escalation via MSI installer Repair mode.