In Qt through 5.14.1, the WebSocket implementation accepts up to 2GB for frames and 2GB for messages. Smaller limits cannot be configured. This makes it easier for attackers to cause a denial of service (memory consumption).
The Google V8 engine, as used in Google Chrome before 44.0.2403.89 and QtWebEngineCore in Qt before 5.5.1, allows remote attackers to cause a denial of service (memory corruption) or execute arbitrary code via a crafted web site.
The GIF decoder in QtGui in Qt before 5.3 allows remote attackers to cause a denial of service (NULL pointer dereference) via invalid width and height values in a GIF image.