A flaw was found in QEMU's websocket I/O channel (QIOChannelWebsock in io/channel-websock.c). The websocket server reads encoded data from a connected client into an input buffer and decodes it into a separate buffer, but the size limit is enforced only on the encoded-input buffer and not on the decoded-input buffer. A client that connects to a QEMU websocket endpoint — such as a VNC server or a character-device socket backend configured with websocket=on — and sends data that is not consumed can cause the decoded-input buffer to grow without bound, exhausting host memory and leading to a denial of service.