An issue was discovered in Qt through 5.12.9, and 5.13.x through 5.15.x before 5.15.1. read_xbm_body in gui/image/qxbmhandler.cpp has a buffer over-read.
Qt 5.12.2 through 5.14.2, as used in unofficial builds of Mumble 1.3.0 and other products, mishandles OpenSSL's error queue, which can cause a denial of service to QSslSocket users. Because errors leak in unrelated TLS sessions, an unrelated session may be disconnected when any handshake fails. (Mumble 1.3.1 is not affected, regardless of the Qt version.)
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).