CVE-2023-6683 Qemu: vnc: null pointer dereference in qemu_clipboard_request()

A flaw was found in the QEMU built-in VNC server while processing ClientCutText messages. The qemuclipboardrequest function can be reached before vncservercuttextcaps was called and had the chance to initialize the clipboard peer, leading to a NULL pointer dereference. This could allow a maliciou...