Qt 6 through 6.6 was discovered to contain a NULL pointer dereference via the function QXcbConnection::initializeAllAtoms(). NOTE: this is disputed because it is not expected that an X application should continue to run when there is arbitrary anomalous behavior from the X server.
https://bugreports.qt.io/browse/QTBUG-115599
http://seclists.org/fulldisclosure/2024/Jan/61
http://packetstormsecurity.com/files/176815/qt-6.6-6.5-6.2-Null-Pointer.html